Contextual reflection (dotnet/coreclr#23740)
* Add ContextualReflection APIs
Add ContextualReflection APIs approved in dotnet/corefxdotnet/coreclr#36236
Fix issue dotnet/coreclr#22213
* SetParentAssembly even when IsCollectible()
* ContextualReflection tests
* PR Feedback
* Add more usage tests
Add using statement tests
Add bad usage tests including Assert.Throws<>
* Only initialize on set
* Add XML API comments
* Unify VerifyIsolation
* Fix unused expectedAssembly
* Remove ContextualReflectionScope throw
* Clean up TestResolveMissingAssembly et. al
* Remove unused QCall::AppDomainHandle
* Remove AppDomainBaseObject
* Pass AssemblyLoadContext as managed object to native
* Fix AssemblyLoadContextBaseObject packing
* AssemblyLoadContext backing stores
Use explicit backing stores for events and properties
* Remove StaticAsyncLocalCurrentContextualReflectionContext
* Remove PermissionSetObject
Commit migrated from https://github.com/dotnet/coreclr/commit/
206f9680303134731862a35338618f2cbd225651