Related to #14592

Move us to SDK 2.2.0 preview

Remove background compiler from TestWorkspace

Avoid allocations in IsDefinedInSourceTree hot paths

Nullable reference types in C# Proposal Link

Move assert outside loop

Need to be on 15.4 in order for the .NET core workload to bring along
the 2.0.0 runtime.

The .NET Core workload brings down the shared runtime component. That is
needed when our core clr tests are run.

Enable execution of well known batch fixer from non-VS host

The abscence of the 2.0.0 shared runtime seems to be the cause of our
CoreClr based suite failures. Hard coding the download of the runtime to
verify this is the case. Will work on a better fix after it's verified.

Fixes #23462

This reverts commit c24e51ef.

Stop publishing VSIXes that don't exist anymore

Assignments can be ref or regular, but there's no such thing as a
"ref-readonly" assignment or "out" assignment, only left-hand sides that
can be ref-kind. Changing to IsRef prevents bugs around looking for the
RefKind of the assignment instead of looking for the RefKind of the LHS.

Move to the officially supported method of disabling transitive project
references for VSIX files.

When looking to see if we have the proper CLI installed for building
need to check the SDK dir, not the CLI directory. This ensures that when
we change SDK versions being used we download the appropriate SDK and
don't accidentally used the previous install.

Well known batch fixer expects a MEF exported IDocumentTextDifferencingService, but we only have one in the EditorFeatures layer.
We already have a simple default differencing service in the workspace, this change exports it at the default service layer.
This change unblocks enabling FixAll testing in roslyn-analyzers repo: https://github.com/dotnet/roslyn-analyzers/issues/1420

Related to #23483

We stop calling string.GetHashCode() at compile time and placing the value in the
generated code because that is not deterministic. Instead we use FNV1a hash code.

For VB, which does not have this bug, we update the implementation to use a more
reliable case-mapping method (see #2116)
Fixes #23020

Remove * from CODEOWNERS file

Remove the uber VSIX

These projects are no longer needed. Removing them.

Historically these were used to create an uber VSIX that nested all of
our other VSIX for a single deployment point. In practice though we have
not actually used these. The install / uninstall issues around them are
too problematic.

Should the uninstall issues be fixed we will consider bringing these
back

Make C# and VB CommandLineParser.Script public

Enable concurrent execution for all built-in C# analyzers