Enable minidumps on all helix runs. (dotnet/coreclr#26455)

Enable minidumps on all helix runs. (dotnet/coreclr#26455)

* Set COMPlus_DbgEnableMiniDump on all helix test runs.

* Set dump output path for *nix builds.

* Enable collecting dumps for timed-out tests on Windows.

* Enable xunit wrapper to get dumps for timed-out tests on non-Windows.

* Use sudo for createdump

* Update coredump-on-crash pattern to use the $HELIX_WORKITEM_UPLOAD_ROOT environment variable.

* Implement linux-specific path for finding a child process by name.

* Use HELIX_DUMP_FOLDER instead of HELIX_WORKITEM_UPLOAD_ROOT

* Remove empty entries in childrenPidAsStrings.

* Look up createdump in Core_Root

* Implement timeout macOS crash dumps.

* Add ulimit -c unlimited to the Helix script on MacOS.

* Get MacOS timeout dumps working (and enable assert/exception dumps)

* Copy OSX aborted test dumps to crash dump folder.

* Add missing return true.

* Allow overwriting dump files on copy (on macOS).

* Fix accidental shadow.

* Allow multiple spaces in ps output.

* Fix dump on windows hitting an assert on checked coreclr.

* TEMPORARY: Add more logging in macOS case.

* Fix change.

* Fix macOS timeout crash dump creation (at least locally).

* Fix Windows timeout dump collection.

* Explicitly use WChar structures.

* TEMPORARY: Test OSX dumps on 10.14 queue.

* Fix __CrashDumpFolder on OSX

* Don't try to copy the dump if it doesn't exist (10.13 Helix queue doesn't support it yet).

* Remove temporary OSX 10.14 queue usage in prs.

* Add tracking issue for empty HELIX_DUMP_FOLDER env var on OSX.

* PR Feedback

Commit migrated from https://github.com/dotnet/coreclr/commit/f5437ac095272f1ab5e8ca79960add974fa96f2d