Nullable enable analyzer driver

Need to account for the case when `GetNextClientConnectionAsync` is
called before the server fully shuts down. The testable host should just
return a `Task` that doesn't complete until `EndListening` completes
(just as the implementation host does)

closes #46758

Fix assert caught in integration tests - compilation event queue may be null at analyzer driver dispose for early cancellation.

Allow TypeScript access to the RemoteLanguageServiceWorkspace

Remove UI thread filtering of code actions

This moves the ref assembly resources display in solution explorer to be
hierarchical based on the target framework that they came from. Prior to
this all of the assemblies were just dumped into the root of the project

Merge release/dev16.8 to master

Merge release/dev16.7 to release/dev16.8

Closes #46431

Merge remote-tracking branch 'upstream/release/dev16.7' into merges/release/dev16.7-to-release/dev16.8

Merge features/function-pointers into master

The `CancellationTokenSource.Cancel` method can throw and that needs to
be accounted for. This exception is not coming from our code but rather
it's coming from the framework code. It is attempting to access a
disposed handle when cancellation IO operations and that results in an
unhandled exception.

This can't really be prevented on our part. We just need to handle it.

closes #46724

* Move remoting infra to Remote.Workspaces

* Fix remote compositions

* Refactor TestWorkspace factories

* Fix remote tests

* Add Remote.Workspaces to VSIX

* Remove unnecessary dependencies

* Add example that reports diagnostics

* upstream/master: (37 commits)
  Lint
  Fix failure to apply timeout in WaitForAllAsyncOperations
  Additional code cleanup
  Fix file headers in default code cleanup
  Update TestRunner.cs (#46690)
  Make Format Document an explicit item in Code Cleanup
  Extract test helper GetDefaultDiagnosticAnalyzerService()
  Simplify type checks.
  Fix crash when typing in an indexer.
  Enforce DoesNotReturn on return; (#46659)
  Disable code fix assemblies during builds
  Expose generator internals: (#46296)
  Address feedback
  Address feedback + fix test
  Update to Microsoft.Net.Compilers.Toolset 3.8.0-2.20408.4
  Add work item attributes
  Add a new command line switch to skip analyzer execution
  Add restricted IVTs for IntelliCode
  Update to Microsoft.CodeAnalysis.Testing 1.0.1-beta1.20407.3
  Finish conversion to new test library
  ...

Remove prototypes and fix a small bug

Extract test helper GetDefaultDiagnosticAnalyzerService()

Fix failure to apply timeout in WaitForAllAsyncOperations

Fix crash when typing in an indexer.

File header cleanup

Closes #46487

* Update TestRunner.cs

* Update TestRunner.cs

Closes #43258