Merge master to master-vs-deps

This change removes the following APIs:
- TypeSymbol.BaseType
- TypeSymbol.Interfaces
- TypeSymbol.AllInterfaces
- NamedTypeSymbol.TypeArguments
- TypeParameterSymbol.ConstraintTypes

These APIs simply delegate the work to APIs with "NoUseSiteDiagnostics" suffix and are not supposed to be used inside compilers. They were left in the code-base because they used to be part of the public surface and the names were nicer, but they are no longer part of the public surface.

* Suggest stackalloc keyword in Span legal places

* Address PR Comments

* More PR Feedback

* Clean up

Remove the TestUtilities Desktop / CoreClr projects

The conditional build of net45 was added when we didn't support any
desktop targetframeworks on Linux. Now that it's supported we should be
building all flavors of the utilities there.

Merge master to master-vs-deps

* Pass in optional arguments by ref

* IOperation tree tests

* PR Comments

Fix the blob publishing

Merge master to master-vs-deps

The dotnet CLI has been seeing a hang from VBCSCompiler in their build
on non-Windows platforms. The cause is this:

    1. dotnet build starts a child process to do `dotnet pack` and
    redirects its output to a buffer.
    2. `dotnet pack` starts a child process to do `compile`.
    3. `compile` starts vbcscompiler because one is not already running.
    4. VBCSCompiler inherits the output handles from (1).
    5. VBCSCompiler process finishes and processes (1) and (2) exit.
    6. The parent `dotnet build` process  is waiting for (2) to exit,
    which it has, but also to see EOF on its output stream. Because that
    stream has been captured and held open by VBCSCompiler, the EOF
    never comes.
    7. `dotnet build` hangs.

This change fixes the problem by creating new streams for input and
output for the compiler server process. This isn't quite what we do on
Windows -- on Windows we create invalid handles for the input and output
-- but it's as close as we can get using the portable APIs in
System.Diagnostics.Process.

Fixes #23734

Remove vs-integration tests from master-vs-deps branch

* Source packages improvements

* Target net45

* Only generate source link when emitting PDBs

* Make BuildBoss happy

Merged it into the non-desktop specific project. Will make porting our
test projects to netcoreapp easier.

The portable test utilities project already multi-targets between
netstandard, netcoreapp and desktop. Having part of the desktop code
exist in a separate assembly makes it even harder to multitarget our
test projects. Combining them all together and fully embracing
multitargeting here.

This is in preparation of moving several other compiler test projects to
test against coreclr / mono.

The tests are dependent on 15.5 but this branch has been updated to 15.6 so the tests are now failing.  Removing until they are fixed.

Remove verbosity flag to dotnet nuget push

fixed issue where same analyzer reference is installed in both vsix and nuget. deduplication in inproc analyzer manager wasn't present in OOP case. (#23772)

this doesn't address our workitem to merge those two. that work is a separate work item. this just follow what we currently do in proc.

Correctly pass --api-key argument to dotnet nuget push

Fix publish-assets.ps1 to call the right helper function

Fix publish-assets.ps1 to call the right helper function

Ensure-DotnetExe should be Ensure-DotnetSdk.

Merge master to master-vs-deps

Merge features/vs-for-mac-refactorings into master