Fix SerialStream.Flush on Unix (dotnet/corefx#40896)

* Fix SerialStream.Flush

* Only wait for write queue to drain on Flush

* add test case with reproted scenario

Commit migrated from https://github.com/dotnet/corefx/commit/45dba6ea7a49a9945a5ad497cfc3de2ec1246683

JsonDocument documenation fix (dotnet/corefx#40994)

* JsonDocument documenation fix

* comma added

Co-Authored-By: Ahson Khan <ahkha@microsoft.com>
Commit migrated from https://github.com/dotnet/corefx/commit/0354194175bb8d609000b463f402942db7235f0a

Given examples and made points explicit (dotnet/corefx#41012)

Made certain points explicit by giving examples or specifying acronyms in brackets where the words they stand for, appear for first time.

Commit migrated from https://github.com/dotnet/corefx/commit/76f566a281bbe979e80cbbb3a48ddf522cdcb4e1

Avoid MemoryMarshal.Cast when transcoding from UTF-16 to UTF-8 while escaping in Utf8JsonWriter. (dotnet/corefx#40996)

* Avoid MemoryMarshal.Cast when transcoding from UTF-16 to UTF-8 while
escaping in Utf8JsonWriter.

* Fix white space typo in the test expected string.

* Guard against empty spans where an implementation of JavascriptEncoder
might not handle null ptrs correctly.

* Cleanup tests to avoid some duplication.

* Some more test clean up.

Commit migrated from https://github.com/dotnet/corefx/commit/ee9995f31b684a0c6e5488eceb2500bf0057da89

Use slow path for CallInstruction returning enum value (dotnet/corefx#40976)

* Use slow path for CallInstruction returning enum value

* Fix assert

Commit migrated from https://github.com/dotnet/corefx/commit/f2daf45473553c19cc7b3dd4bb3f2033080a254c

Delete unused ItemGroup (dotnet/corefx#40983)

Moved to CoreLib

Commit migrated from https://github.com/dotnet/corefx/commit/0ebca43a4db8d5ddaf2e9fd0df359a262b61c0ce

Re-enable macOS 10.13 (dotnet/corefx#40980)

Commit migrated from https://github.com/dotnet/corefx/commit/7b0e8cc8d66275de148f7310a7116de00d814cd0

Fix namespace typo in Tasks test (dotnet/corefx#40974)

Commit migrated from https://github.com/dotnet/corefx/commit/02bebd69dcac53a7b903d605ce43fd28cd5ee0e9

Add test for IComponent typeconverter register in TypeDescriptor (dotnet/corefx#40959)

Commit migrated from https://github.com/dotnet/corefx/commit/d1eeba90af85dd203aa27adbb30a28e45b54e23d

Add CodeDom.CodeValidator tests and fix some bugs (dotnet/corefx#39585)

* Add CodeDom.CodeValidator tests and fix some bugs

* Fix netfx tests

* PR feedback

Commit migrated from https://github.com/dotnet/corefx/commit/50e8db3cabbfb6ad0fc0702b3db25491a95c72a5

Minor deserialization perf improvements for collections (dotnet/corefx#40889)

Commit migrated from https://github.com/dotnet/corefx/commit/27ddbe99ccc32122141b81045ac670c3a0d1a45a

Writable JSON API changes (dotnet/corefx#40673)

* implicit operators moved to JsonNode
* JsonNull introduced
* JsonObject rewritten to use JsonObjectProperty
* JsonElement.ObjectEnumerator changed to use _current instead of _enumerator
* iterative DeepCopy implemented
* code reorganized
* parse implemented
* JsonDocumentOptions added to JsonNode.Parse
* WriteTo and ToJsonString added
* specification adjusted
* string comparison added
* JsosReadonlyDomWriteTests reused
* code coverage improved
* minor other fixes
* review comments included

Commit migrated from https://github.com/dotnet/corefx/commit/37b37395481b635c15eaa3454e52b72ab91de4ef

Allow more of ConsolePal to be linked away (dotnet/corefx#40944)

If an app just uses Console.Write*, it's currently still pulling in support for stdin and stderr, because of the GetUseFileAPIs choke point.

Commit migrated from https://github.com/dotnet/corefx/commit/d733b29ce6fccd7e64bc351e97cce68a9b91bb17

Use ThrowHelper in Utf8JsonReader.GetGuid so that the deserializer can catch the exception and re-throw JsonException. (dotnet/corefx#40938)

* Use ThrowHelper in Utf8JsonReader.GetGuid so that the deserializer can
catch the exception and re-throw JsonException.

* Fix the typo in the enum used and added more test cases.

Commit migrated from https://github.com/dotnet/corefx/commit/5bec8c841ec0ab366a99361bc9d4540022e7fa02

Replace HashHelpers.Combine with HashCode.Combine in netcoreapp projects (dotnet/corefx#40935)

Commit migrated from https://github.com/dotnet/corefx/commit/8c221ca346b64e1e80ab4bde240b0f479bd203fc

Mark System.Data.SqlClient as archived component (dotnet/corefx#40946)

Commit migrated from https://github.com/dotnet/corefx/commit/f5574287ee7e9ef785ee6849bad7916871bebd81

Remove ProjectGUIDs from project files and Project and Name attributes from P2Ps (dotnet/corefx#40926)

* Remove ProjectGUIDs from P2Ps

* Remove ProjectGUIDs from project files

Commit migrated from https://github.com/dotnet/corefx/commit/c22714d65151968a17c3b232748880d5e7961dee

fix of a minor typo in System.Threading.Channels.ChannelReader docs (dotnet/corefx#40943)

Commit migrated from https://github.com/dotnet/corefx/commit/061d05b8df6295a9253d2bae423d89538a3b9132

Add tests relating to TypeDescriptor (dotnet/corefx#38938)

Commit migrated from https://github.com/dotnet/corefx/commit/cc51975a897cb803f1ad76b6b93b2ebd4581bca4

Cleanup drawing primitives (dotnet/corefx#40019)

Commit migrated from https://github.com/dotnet/corefx/commit/5bc243aa2040a1dbf63df1dd099124ade64ed5ce

Add more TypeConverter tests (dotnet/corefx#38945)

* Add more TypeConverter tests

* Add more ReferenceConverter tests and fix bugs

Commit migrated from https://github.com/dotnet/corefx/commit/ae987068bb07d7b8af458874d74714083a84618c

Disable OSX.1013.Amd64.Open in CI (dotnet/corefx#40927)

Commit migrated from https://github.com/dotnet/corefx/commit/f0d5faf69b832646240b1b30797587ab35ffd03b

Increase helix timeout on Windows clients (dotnet/corefx#40913)

* Increase helix timeout on Windows clients

Depending on the ARM64 windows queue utilization, clients sometimes take longer than the current timeout. Increasing temporarily until the queue has more machines.

* Update windows.yml

* Update windows.yml

Commit migrated from https://github.com/dotnet/corefx/commit/ba5b90b95269548f8011e36e13b7f58acb62b4b8

Add missing dummy primitive to ReadOnlySequence<T>.Enumerator (dotnet/corefx#40910)

Commit migrated from https://github.com/dotnet/corefx/commit/59c6b1ab96aa2e99ed6ecb33a8bcf9283ce1ea27

Remove Redundant dependency of microsoft.netcoreapp.platforms  (dotnet/corefx#40907)

* remove extra dependency

* removing microsoft.netcore.targets

Commit migrated from https://github.com/dotnet/corefx/commit/9e8d47c6e548dcacd71cb83133bbf49f74be90ac

Disable ToolboxBitmatAttribute test in netfx (dotnet/corefx#40901)

Commit migrated from https://github.com/dotnet/corefx/commit/937e7d6d7eb6f1413aa48d14961d8f0c8a061e0e

Fix Select.Count bug that iterates twice (dotnet/corefx#40718)

* Add System.Linq tests to validate enumerator lifecycle

* Fix bug with Select(...).Count() on an IPartition

It currently ends up potentially enumerating the source twice.

* Remove unnecessary source inputs in lifecycle tests

Commit migrated from https://github.com/dotnet/corefx/commit/8455fd2d9bd46fc8b97fe86f907d2a8ae748443f

Remove misleading test condition variable for registry (dotnet/corefx#40887)

Commit migrated from https://github.com/dotnet/corefx/commit/d88152f91a5b08534873868afe93ddc3c840f76f

Disable two flaky EventLog tests (dotnet/corefx#40876)

Commit migrated from https://github.com/dotnet/corefx/commit/9d5b200c6088d9dc038c64ec051596170731dbab

Make "remote" more CultureInfo.CurrentCulture setting tests (dotnet/corefx#40891)

Commit migrated from https://github.com/dotnet/corefx/commit/002d62b53343ae9b24310681c349913b97d30202

Disable two networking tests on UAP (dotnet/corefx#40875)

* Disable timeout sensitive networking test on UAP

Disabling GetAsync_CancelPendingRequests_DoesntCancelReadAsyncOnResponseStream on UAP

* Update HttpClientHandlerTest.Cancellation.cs

Commit migrated from https://github.com/dotnet/corefx/commit/9161098ade5075a8c126b2d7eb98abbeadff2961

Fix some low-hanging fruit boxing in JsonSerializer (dotnet/corefx#40867)

It's boxing lots of dictionary enumerators and KeyValuePairs.  Stop doing that.

Commit migrated from https://github.com/dotnet/corefx/commit/447f76f251d72a6d5e9bc102523937d05f929095

Add license header to S.R.CS.Unsafe (dotnet/corefx#40886)

Commit migrated from https://github.com/dotnet/corefx/commit/b42c65ee76c35a63124a6b8e887bbd25c0d263df

use type for Http2LoopbackServer.CreateServer (dotnet/corefx#40863)

Commit migrated from https://github.com/dotnet/corefx/commit/b46ebcb9a2408f9826c103ce6b340b419d948512

update SendAsync_ConcurentSendReceive_Ok to use DuplexContent (dotnet/corefx#40858)

Commit migrated from https://github.com/dotnet/corefx/commit/88017f967529d30272ad75028e5538f35087e451

Address a couple non-functional nits (dotnet/corefx#40854)

Commit migrated from https://github.com/dotnet/corefx/commit/4390a665c2fe082007f6bd25be0e055307ee5573

Allow NetworkStream.WriteAsync calls to be canceled asynchronously (dotnet/corefx#40839)

In 3.0 we added the necessary support for this, and for Socket.WriteAsync calls we're appropriately passing the CancellationToken through, but we missed doing so for NetworkStream.WriteAsync, which takes a slightly different code path through AwaitableSocketAsyncEventArgs.

Commit migrated from https://github.com/dotnet/corefx/commit/0a5b9286854c8bbb10677d730b0fe25425da562c

Update Stable Version info on package index (dotnet/corefx#40780)

* Upate Stable Version info on package index

* Re-adding back package version which was unlisted

Commit migrated from https://github.com/dotnet/corefx/commit/95c10ccf3f17e35339070a5ecacdc44366585643

Fix TypeConverter for IComponent (dotnet/corefx#40837)

Commit migrated from https://github.com/dotnet/corefx/commit/3cc18081e24acdcfe7db737400a2dc702e314395

Raise JsonException when PolicyProperty is null (dotnet/corefx#40501)

Commit migrated from https://github.com/dotnet/corefx/commit/5dbbdfa0f924f02754a464d492a2116ad9f5752b

Use options.Encoder when serializing dictionary keys and property names (dotnet/corefx#40787)

Commit migrated from https://github.com/dotnet/corefx/commit/7829d4acc8303a42e222415c7eb829fc3f8264cc

Match src param name of BrotliEncoder.GetMaxCompressedLength to ref param name (dotnet/corefx#40822)

* Make the name of the parameter in the BrotliEncoder.GetMaxCompressedLength src match the name of the parameter in the ref.

* Update unit test validating parameter name.

Commit migrated from https://github.com/dotnet/corefx/commit/c668e96cb0886d13a051d8021a3c3147e7daa15c

Support PAC scripts that return multiple proxies (dotnet/corefx#40082)

* Support PAC scripts that return multiple proxies.

Resolves dotnet/corefx#39370

Commit migrated from https://github.com/dotnet/corefx/commit/5e97c2b50ac2b18909606ce3ea14c3e7e61db7e8

Reduce number of PFX loads in System.Net tests (dotnet/corefx#40821)

* Reduce number of PFX loads in System.Net tests

* Address PR feedback

Commit migrated from https://github.com/dotnet/corefx/commit/838832e2ecac9f81b5a5649bfac2fc835db76c1e

Fix | SqlClient fix for managed encryption connection failure (dotnet/corefx#40732)

Commit migrated from https://github.com/dotnet/corefx/commit/30decee8aa72ce93eec0394e94f05a86cec7ab9d

fix more tests to work with http2 (dotnet/corefx#39019)

* fix cancelation tests to work with http2

* fix more tests and feedback from review

* feedback from review

* fix issues with missing connection: close

* update body check

* feedback from review

* fix resolve

* feedback from review

Commit migrated from https://github.com/dotnet/corefx/commit/5108d9245b891deeb36a164f434f4fb6975c8baf

Add round-trip test to JsonSerializer with overflow that needs to be escaped. (dotnet/corefx#40793)

* Add round-trip test to JsonSerializer with overflow that needs to be
escaped.

* Used escaped property names and add a test for serializer/writer
interop.

Commit migrated from https://github.com/dotnet/corefx/commit/76031d2f8ed714b54e0e7bbd7020f111b6c9c023

Remove `readonly` from two `GCHandle` fields (dotnet/corefx#40807)

Due to the `readonly`, the mutations performed by `Free` will be done on a copy rather than on the data stored in the field.

Commit migrated from https://github.com/dotnet/corefx/commit/437ce88edeb835e1dbe94c6d418b6169b69745fb

Delete Box.cs from System.Threading.Tasks.Parallel (dotnet/corefx#40808)

We can just use `StrongBox<T>`.

Commit migrated from https://github.com/dotnet/corefx/commit/0b572f1a7ec2f691a424d0c6dd403e11191ca8c5

Remove reflection from ThreadPoolHelpers test class (dotnet/corefx#40810)

Commit migrated from https://github.com/dotnet/corefx/commit/c9a124635dbfc0ec3958f06093cd5196b00b47b1

Disable FileSystemWatcher_File_Create_ForceLoopRestart test (dotnet/corefx#40804)

Commit migrated from https://github.com/dotnet/corefx/commit/aea8a56edf54228029b0f9ddf369e4d4f82f4446

Move wildcard bind in Socket.ConnectAsync to be Windows-only (dotnet/corefx#40767)

* Move wildcard bind in Socket.ConnectAsync to be Windows-only

It's necessary to use ConnectEx; it's not necessary on Unix.

* Address PR feedback

Commit migrated from https://github.com/dotnet/corefx/commit/8a1fc9d6b3c9b85a881e220a9f9193b72c0e801b

Fix the max token size threshold to correctly compute to 125MB for Base64 bytes. (dotnet/corefx#40792)

* Fix the max token size threshold to correctly compute to 125MB for
Base64 bytes.

* Rename constant to fix transpose error: Base46 -> Base64

* Enable the outerloop tests for windows and osx only and update to use
platform specific new line.

Commit migrated from https://github.com/dotnet/corefx/commit/1511f723f7adfe82cef72460df45dc4422d303c6

Disable XML crypto test failing on Windows 10 (dotnet/corefx#40775)

Commit migrated from https://github.com/dotnet/corefx/commit/70b4d01e18236c925c2d44d49fff7cbb4919dc43

Fix several recently added StyleCop tuple rules (dotnet/corefx#40794)

Commit migrated from https://github.com/dotnet/corefx/commit/06007cdedee9cfb096d884016a99e3a64bdccb45

DiagnosticSource Stop event was not reported in W3C mode by HttpHandlerDiagnosticListener on netfx (dotnet/corefx#40777)

Commit migrated from https://github.com/dotnet/corefx/commit/687a84008e6c532584199305a75ec53e4e1f1c74

replace CRLF with Environment.NewLine where appropriate (dotnet/corefx#40723)

* replace CRLF with Environment.NewLine where appropriate

* use sb.AppendLine

* fix more unit tests

Commit migrated from https://github.com/dotnet/corefx/commit/a6e7ffd72db078a46612afa9d085bd27ef8e2fed

surface _abortException (dotnet/corefx#40785)

Commit migrated from https://github.com/dotnet/corefx/commit/bc7e561e28839c56f7465f3382d5f60716a34bab

Add case-sensitive type lookup test to ActivatorTests (dotnet/corefx#40788)

Commit migrated from https://github.com/dotnet/corefx/commit/ffe957980a1c33217d2fca68bb473029f37568e4

Fix JsonElement.WriteTo handling of escaped property names (dotnet/corefx#40784)

This removes the duplicate switch statement from writing properties,
as the usage of the new WritePropertyName API on the writer simplifies the logic here.

Commit migrated from https://github.com/dotnet/corefx/commit/2d2abb32db879c877e14310c892faeeef756e27d

Revert "set _requestQueueBoundHandle to null after disposing" (dotnet/corefx#40783)

* Revert "set _requestQueueBoundHandle to null after disposing (dotnet/corefx#40466)", but keep tests around (disabled re: 39552)

This reverts commit dotnet/corefx@40949c48e1a24a735452248294c983609c77a26c.

Commit migrated from https://github.com/dotnet/corefx/commit/7a668f4f13b962a20a4585fffadbf537d5ebf570

Update analyzer versions (dotnet/corefx#40778)

In particular to pick up StyleCop fixes related to C# 8 and nullability.

Commit migrated from https://github.com/dotnet/corefx/commit/1bf90840626cd2e7b19377bd6a16b17de0e6e672

Add the DebuggableAttribute to System.Runtime.CompilerServices.Unsafe.

Commit migrated from https://github.com/dotnet/corefx/commit/f9c848d6ad5415c1fa844f5403ea8ef78c408f9a

Pass a CancellationToken in a few more places (dotnet/corefx#40715)

Most of these to WaitAsync shouldn't actually matter, as the semaphores being used are there for corner cases or to protect erroneous usage, but if there's no contention, passing a token won't hurt, and if there is contention, passing the token makes it more robust.

Commit migrated from https://github.com/dotnet/corefx/commit/14a7adb23569363b94d575d64b7cb1f38cda3e4a

Fix regression in TCPClient behavior when Disposed/Client set to null (dotnet/corefx#40769)

Commit migrated from https://github.com/dotnet/corefx/commit/e0a6f2b7b11afc2be10a535477910524d9fee834

Disable a couple S.S.Cryptography.Algorithms tests deterministically failing locally

Commit migrated from https://github.com/dotnet/corefx/commit/a533a0fad2c101881945824570dc21845783366a

Disable RsaDecryptPkcs1LeadingZero test failing on some Windows (dotnet/corefx#40760)

Commit migrated from https://github.com/dotnet/corefx/commit/5b2c6b7d286265d3bdaddb8445c1bbf3d9141461

Consolidate / cleanup disposal checks in System.Net.Sockets (dotnet/corefx#40757)

Commit migrated from https://github.com/dotnet/corefx/commit/b2412774416fc177cf5daa025bb4644a0a91c2df

Disable flaky PrintPage test (dotnet/corefx#40754)

Commit migrated from https://github.com/dotnet/corefx/commit/b059630fc9139d0c940b2f0f249ff702a7b6250f

Retry eventlog deletion in tests on all platforms (dotnet/corefx#40743)

* Retry deleting eventlog on all platforms

* Remove OS differentiation

Commit migrated from https://github.com/dotnet/corefx/commit/8c041484dda3059bd4adebebda939a15ee4a087d

Update pull-request-policy.md

Commit migrated from https://github.com/dotnet/corefx/commit/74708406b04b3d0946d53259ddbc93159ac90a24

Delete duplicate line after LINQ nullable changes (dotnet/corefx#40746)

This line was moved into the ctor and should have been deleted from here, too. Addresses post-merge PR feedback.

Commit migrated from https://github.com/dotnet/corefx/commit/71c669e918a5f4e48f09a697e9dd147f7dc31480

Disable TimerElapsedSignaled (dotnet/corefx#40742)

https://github.com/dotnet/corefx/issues/29166

Commit migrated from https://github.com/dotnet/corefx/commit/a44c40809c43d29ab3d42d5e6a7d8ad1b65a4fe6

Update pull-request-policy.md

Commit migrated from https://github.com/dotnet/corefx/commit/1d994feb73fcf57161e5bded92119c0d1b147616

Update pull-request-policy.md

Commit migrated from https://github.com/dotnet/corefx/commit/49e2b4955ff83acc4b19b503709bd1e56f409871

Create pull-request-policy.md (dotnet/corefx#40701)

* Create pull-request-validation.md

* Update pull-request-validation.md

* Update pull-request-validation.md

* Update pull-request-validation.md

* Update pull-request-validation.md

* Rename pull-request-validation.md to pull-request-policy.md

* Update pull-request-policy.md

Commit migrated from https://github.com/dotnet/corefx/commit/e2a3e98ee0ae608783906c3a352be27bf7e437b6

Simplify BitArray enumerator (dotnet/corefx#40735)

Commit migrated from https://github.com/dotnet/corefx/commit/130d8582e4973bbdb55ae737b942d214ad3c6570

Add tests for round trip serializing TimeZoneInfos. (dotnet/corefx#40637)

Fix dotnet/corefx#40578

Commit migrated from https://github.com/dotnet/corefx/commit/75a591d4e5606c49f00e187ea2f5ba694d712523

Add harvest validation logic to the all configurations tests (dotnet/corefx#40717)

Commit migrated from https://github.com/dotnet/corefx/commit/2c974d484209ab46815ec9abd35936ca66f2444e

Skip tests on Arm (dotnet/corefx#40716)

Commit migrated from https://github.com/dotnet/corefx/commit/c1974096f6e02099a7e4d030ce0dd903574dd24e

Annotate System.Threading.Channels for nullable reference types (dotnet/corefx#40653)

Commit migrated from https://github.com/dotnet/corefx/commit/60e5e452977d0c51bd8c20e6c390f47333ad85b9

Tests for abbdrivated genitive month names parsing (dotnet/corefx#40595)

Commit migrated from https://github.com/dotnet/corefx/commit/e62f9b61785a340a4a73182c2e228d6ef409dec4

Disable TestZeroTimeout hanging test (dotnet/corefx#40713)

In response to https://github.com/dotnet/corefx/issues/40711

Commit migrated from https://github.com/dotnet/corefx/commit/5fef8a05c2ba51b614dbc2d5350fc3cc0e8541b4

Httpstress: Add more checksum validations & expose Kestrel Http2 limits configuration (dotnet/corefx#40708)

Httpstress: Add more checksum validations & expose Kestrel Http2 limits configuration

Commit migrated from https://github.com/dotnet/corefx/commit/a64e40535283d6470c2909c8f08b178454a8718b

Annotate System.Linq for nullable reference types (dotnet/corefx#40651)

Commit migrated from https://github.com/dotnet/corefx/commit/fe969a5893b845c0ba4550d828894c49745f456f

Fixed missing Dispose call on Union on empty enumerable (dotnet/corefx#40384)

Commit migrated from https://github.com/dotnet/corefx/commit/e78caf82ce13b6e1d1359cc239bf0535943cc386

Annotate Microsoft.Win32.Primitives for nullable reference types (dotnet/corefx#40652)

Commit migrated from https://github.com/dotnet/corefx/commit/70d2b62dcfd328228f8ea6754faae0ed3b69ff37

Test for ArrayPool.Create allocating cleared arrays (dotnet/corefx#40592)

Commit migrated from https://github.com/dotnet/corefx/commit/eeca0c2c0876919a9029cfdc371070bba84da02b

Tests for Read_CharArrayTest reading more than necessary (dotnet/corefx#40521)

* Tests for Read_CharArrayTest reading more than necessary

* Update src/System.IO/tests/BinaryReader/BinaryReaderTests.cs

Co-Authored-By: Stephen Toub <stoub@microsoft.com>
Commit migrated from https://github.com/dotnet/corefx/commit/a192823a84145546be747cc520625062fe6cb5a8

Limit precision checks in arm/64 (dotnet/corefx#40696)

Commit migrated from https://github.com/dotnet/corefx/commit/6e01a780a8a5bc61332c8d743e8516c15bbbb293

Net.Http Use span.SequenceEqual rather than custom EqualsOrdinal (dotnet/corefx#40694)

* Net.Http Use span.SequenceEqual rather than custom EqualsOrdinal

* Fix tests

Commit migrated from https://github.com/dotnet/corefx/commit/d3cd1d05357d3c5f756a89d9800af6ef91dd8efe

Ignore casing in servicename tests on nano server (dotnet/corefx#40699)

Commit migrated from https://github.com/dotnet/corefx/commit/0c650b2765f64186f2fe84e332d8a74108866db2

Update pullrequest-builds.md

Commit migrated from https://github.com/dotnet/corefx/commit/261b2cdc260bc94967a8af6666831739d91ceb96

Disable EventLog failing test on Windows (dotnet/corefx#40688)

Relates to dotnet/corefx#40224

Commit migrated from https://github.com/dotnet/corefx/commit/ae0d0cb852a6186ca5ef8130b0bf862314485017

Disable two flaky tests Mutex/Netw (dotnet/corefx#40689)

Commit migrated from https://github.com/dotnet/corefx/commit/3ef9df83a04113947c42d69cef4b7aadedd612c6

Deserialize extension data properly for child objects (dotnet/corefx#40662)

Commit migrated from https://github.com/dotnet/corefx/commit/26782185622fde9ba354a3decd42f9a0a1a1a266

Enable macOS10.14 in PR builds (dotnet/corefx#40684)

Commit migrated from https://github.com/dotnet/corefx/commit/7e5791b9fb20e29b5fbf8d89ff2688663ae9310a

SmtpClient: fix Timeout for low values (dotnet/corefx#37462)

* SmtpClient: fix Timeout for low values

The timeout is triggered from a Timer.
There were two race conditions:
- The timer event could occur before there was a connection to abort.
- The connection abort performs a TcpClient.Dispose, which may not
work when there is a TcpClient.Connect occurring simultaneously.

* TCPClient: make Dispose thread-safe

* Fix NullReferenceException from _networkstream.Close

* SmtpTransport: fix racy aborted detection

* TestZeroTimeout: skip on .NET Framework

* PR feedback

* Don't null out socket on Dispose to let ODE propagate from Socket

* Fix merge

* Run TestZeroTimeout test on Linux too

* Add back ODE to TcpClient.Connect(IPEndPoint)

* Add comment about why we're disposing the socket

* PR feedback

Commit migrated from https://github.com/dotnet/corefx/commit/807a18da803b09cdca42bfb7d05652b843f5079b

Add custom enum converter test for having flags as array (dotnet/corefx#40678)

Commit migrated from https://github.com/dotnet/corefx/commit/e3644c538ab5dad6c19c6a7c975df0b160823875

changing netcoreapp targetframework from 3.0 to 5.0 and adding support for targetgroup = netcoreapp5.0 (dotnet/corefx#40049)

* adding 5.0 target moniker

* Restoring packages for netcoreapp3.0

* package config for crypto done

* Drawing.Common and System.Windows.Extensions done

* some left over crypto and some smaller other libraries

* security.permissions, WindowsRuntime, WindowsRuntime.Xaml done

* experimental projects and openssl cryptography

* harvesting the runtime package  version for windows Runtime

* update VS configurations

* reverting the shared framework package

* some remaining  projects

* Using sdk to restore package and targetFrameowrk for netcoreapp3.0

* removing harvesting and using ReferenceFromRuntime for windowsRuntime project

* For oob packages with no pkg folder

* addresses feedback

* addresses the feedback

* reverting a commit with extra packageconfig additions

* System.text.Encoding.Web configurations edited

Commit migrated from https://github.com/dotnet/corefx/commit/777dbdec193fcbe49b3f18614348ac96f77d57c3