Set ApplyNgenOptimization in bootstrap compiler build

Merge dev16.1-preview1 to master

* fixed issue where we crash due to our pending async work run after VS shutdown

this is another case where we have a pending async task that run after VS shutdown and it throws and our fail fast code catch that exception and crash VS.

general fix will be some thing like us making our fail fast code to aware shutdown situation and ignore any exception if we are in the shutdown situation.

but until we come up with proper design, this should handle one of high watson hits.

* PR feedbacks

Fix flaky test AsynchronousOperationListenerTests.IgnoredCancel

Make struct types readonly in Microsoft.CodeAnalysis.Features

Merge Default Interface Methods feature into master

Verification for VS.ExternalAPIs.Roslyn package

Add ExternalAccess assembly for unit testing

Workaround a CLR deadlock caused by unloading app domains with STA RCWs

Run CI on dev16.1-preview1 branches

Merge dev16.1-preview1 to master

A recent refactoring caused a number of insertion failures as we weren't
properly updating the contents of VS.ExternalAPIs.Roslyn.nupkg. This
adds basic verification that the contents are correct based on our build
output.

* Added CSharp.Scripting to VS.ExternalApis pacakge

* Add ExternalAccess to VS.ExternalApis package

Merge dev16.1-preview1 to master

Merge 'dotnet/master' into DefaultInterfaceImplementation

Fix build correctness

Fix focus of items
Fix accelerator key duplication
Narrator reads the datagrid correctly

The project which deploys ILASM tools ends up bringing two runtime
packages that have the same assets:

- runtime.win-x64.microsoft.netcore.runtime.coreclr
- runtime.win-x64.microsoft.netcore.app

Specifically assets like SOS.NetCore.dll exists at different versions in
these packages and end up getting copied twice to the output directory.
This double write ends up breaking our build (as well as basic
isolation).

The short term fix here is to no longer treat this as a code project but
instead a tools project. That eliminates the MS.NetCore.app package and
the associated double writes

Long term though the root issue needs to be addressed: making ilasm and
ildasm easier to deploy.

https://github.com/dotnet/coreclr/issues/15059

Remove duplicate PackageReference