There are a few parts to this change:

1. Ensure that MSB3270 and MSB3277 warnings are promoted to errors in CI
and hence block merging.
1. Move our DiaSymReader.Native logic into a separate targets file.
This resource cannot be consumed with a simple package reference but
rather requires a package reference and custom logic to pull out the
contained binaries. This logic used to be spread through our build. Now
it's in a single place.
1. Remove the x86 bootstrapping logic. This was testing a pretty obscure
scenario and the cost of maintaining that logic is siginificant at this
point. Can bring back if we ever find a bug in this area.

The root cause of the MSB3270 warnings is a subtle change in the SDK. It
now passes the runtime graph to NuGet for native assets. In the case of
DiaSymReader.Native there are runtime specific assets hence the SDK /
NuGet had to pick one for framework projects. This eventually lead to
`PlatformTarget` being set to x86 where it shoud have been AnyCPU.

Part of the change includes adding `ExcludeAssets=all` to the package
reference which means they no longer figure into this logic and hence
the binaries are marked as AnyCPU.

This regression in behavior is being tracked by
https://github.com/dotnet/sdk/issues/3495

Merge release/dev16.3-preview2 to master

UseExpressionBody cleanup

Update signing cert used for EE.ResultProvider - 16.3 P2

Update signing cert used for EE.ResultProvider - 16.3 P3

Add tests for RefaHelpers with empty Attributes / empty decls. 

Merge release/dev16.3-preview2 into master

Skip BasicEditAndContinue integration tests that are failing

* Cleanup

* Optimize memory allocation of LCS algorithm

Merge pull request #37594 from jasonmalinowski/add-nullable-annotations-to-speculative-model-creation

Add nullable annotations to speculative model creation and update code for bug found

Merge release/dev16.3-preview1 to master

Update some skip attributes on TypeInferrer tests

Consume the new compiler API for comparing symbols without nullability

Fix using statements to use correct copy of PooledObjects

Fix trailing whitespace and superfluous blank lines in generated GlobalSuppressions.cs

Add an integration test for #37623

* EE: Do not trim comments from expression preceding a quote

Deserialize to VSClientCapabilities

Adds a typing integration test for https://github.com/dotnet/roslyn/pull/37623. Primary bug fixed in the PR: VSO [#957250](https://devdiv.visualstudio.com/DevDiv/_workitems/edit/957250). I verified that the test fails consistently without the fix in #37623 and passes consistently after the fix.

My previous PR #37303 to improve IDE open file analysis performance led to a functional regression where attempting to compute open file diagnostics for a partial type leads to recursive attempt to force complete all partial trees, which in turn attempt force completion of original tree. In presence of cancellation request, this leads to a stack overflow and VS crash. The fix here ensures that we don't attempt partial tree analysis when invoked in context of partial analysis itself.
Fixes VSO [#957250](https://devdiv.visualstudio.com/DevDiv/_workitems/edit/957250) and [#957243](https://devdiv.visualstudio.com/DevDiv/_workitems/edit/957243)
Fixes #37567

I have manually verified the crash before the fix and verified it does not repro after the fix. I am working on adding an integration test for the scenario with a follow-up commit/PR.

 Recognize existing GlobalSuppressions.cs when it has a using directive 

Add back typescript gotodef on the client.

Merge release/dev16.2 to release/dev16.3-preview1

The Microsoft.CodeAnalysis.FlowAnalysis.Utilities assembly which we
consume accidentally made it's copy of the PooledObjects helper public.
That copy has a different namespace, so by using the wrong namespace
we were pulling in that assembly's copy rather than using the copy we
have in our assembly. This causes us to do an early assembly load when
it's absolutely not necessary.

Use expr/block body lambda simplification