Merge release/dev16.3 to release/dev16.3-vs-deps

Extract method will now maintain nullable reference types for parameters and return types. If the parameters or return types are determined to be non-nullable through flow state analysis, then we will adjust them to be non-null when generating. 

For return type, the adjustment is done after the method is generated. This is because the generator can and will introduce new return statements that need to be analyzed for null state. The only way a return type can be modified to non null is if it:

1. Was null annotated to start with
2. All returns are determined to return non-null by flow state analysis. 

Similarly, reference parameters can be assigned null or non-null values inside a method. We determine parameters can be adjusted if:

1. Null is not passed into the parameter.
2. Null is never assigned to the parameter. 

Remove the 7.3 languageversion from the BindSymbolInOtherFile test

Merge master to master-vs-deps

Handle escaping of ref/out parameters on non-regular CFG exit paths (…

Merge master to master-vs-deps

Remove inaccessible attributes when generating code

Show nullable annotations in tuple signature help

Update Generate Equals and GetHashCode to handle nullable members

Do not fade code for IDE0016 (UseThrowExpressionDiagnosticId)

Revert test workarounds/skip for IDE diagnostic configuration code fixes

- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19419.12

Most of the tests in here still hard code older baselines because they
predate some pattern matching improvements, but this is fully new.

Fixes https://github.com/dotnet/roslyn/issues/37913

Fix generated Equals(object) parameter nullability mismatch

Fixes https://github.com/dotnet/roslyn/issues/37252

Remove RuntimeIdentifiers

Disabling Mono leg

Latest Mono nightly builds appear to have broken serialization during
remoting across AppDomain instances. That is pretty fundamental to how
we test. Temporarily disabling the Mono leg until this can be fixed.

Tracking Mono Issue: https://github.com/mono/mono/issues/16373

If you forget to wrap something in a <Document> then this can flag
where you did that.

Also add a few more places where we need to wrap symbols.

It turns out for methods we already had
RemoveInaccessibleAttributesAndAttributesOfTypes but had accidentally
created another helper for filtering out attributes from parameters
that more correctly should have used that. This also observed that we
didn't have a helper for IParameterSymbols to do the same thing.
We did have one that filtered but not one that removed innaccessible
parameters, which was actually a bug.

We had a helper for 'create an IMethodSymbol with certain changes', but
it didn't have quite enough that we could use it in more places. Also
inline it into the single caller.

Convert Get/Set property fixed to handle nullability

If you write a test to assert a code fix works, and you don't get a
code fix, sometimes that's because the code fix is broken. Sometimes
it's just because you have a silly typo in your test that means the
test workspace isn't doing what you think. To aid in debugging those,
add some extra test support to dump diagnostics in that case.

Update override completion for nullable reference support

The `$(RuntimeIdentifiers)` property was added some time ago to support
scenarios like self contained in our infrastructure. That is no longer
done during build and this property is no longer necessary. Further it's
causing us additional restore time to bring down runtimes we don't need.

Merge release/dev16.3-preview2-vs-deps to master-vs-deps

Merge master to master-vs-deps

Fixes #27213

Analyzer recommends using throw expression for null checks instead of throw statement within an if statement with null check. We used to fade the entire if statement for discoverability and increased code fix span, but this was undesirable as we want to fade only unnecessary or dead code. This change removes the fading diagnostic and updates unit tests accordingly

This reverts commit ed6a2b81.

Move to a new Windows pool

Convert To Interpolated Strings refactoring provider should treat cha…