Expose `Iscollectible` property on Assembly and MemberInfo (dotnet/corefx#33979)

Expose `Iscollectible` property on Assembly and MemberInfo (dotnet/corefx#33979)

* Expose IsCollectible on MemberInfo

* Adding skeleton for testing IsCollectible property on MemberInfo/MethodInfo

* Add test for generic tests being loaded using Assembly.LoadFrom

* Expose IsCollectible on Systme.Reflection.Assembly

* Adding tests for generics with type parameters from collectible assembly

* Rename test class to be more general

* Removing unnecessary comments

* Add test skips for uapaot

* Add missing Dispose() to tests

* Fix typos and add framework exclusion for NetFx

* Simplify TestAssemblyLoadContext.Load() per feedback

* Finish simplification of TestAssemblyLoadContext and added statics to tests

* Prevent IsCollectible tests from compiling on netfx

Commit migrated from https://github.com/dotnet/corefx/commit/d38db578d8a611f28a62de1005a9299d199bf5a9