While implementing the tests for the ref-reassignment test plan (#22466)
I found a bug in the handling of the ref-escape scope of a ref local in foreach. That bug is fixed
and the rest of the items in the test plan should have a test.

Fixes #22466

* Produce errors on invalid pdbpath supplied to compiler

* More tests

The scenario listed in https://github.com/dotnet/roslyn/issues/22700
demonstrates the problem. The direct cause of the crash is that local
lowering produces two instances of the lambda and lamda conversions in
the resulting bound nodes. This crashes the closure conversion pass
since the same lambda cannot appear in two places in the tree. However,
even if that were allowed, this would violate the language
specification.

Placing a lambda inside an indexer which is nested in a compound
assignment creates two calls which contain the delegate produced by the
lambda expression. If the expression kind is marked as side-affecting it
will be spilled into a temporary variable. However, the local lowering
doesn't distinguish between whether an expression is side-affecting and
whether or not it is referentially transparent. In this case, both
matter. Since the delegate produced by the conversion can be compared by
reference to any other delegate produced by the same lambda, the code
must be referentially transparent -- it must produce the same result
when evaluated repeatedly.

The fix is small: mark lambda conversions as side-affecting. There are
certain cases, like the creation of temporaries for out-of-order calls
with named parameters, where the lambda conversion is only required to
be non-side-affecting instead of referentially transparent, but it does
not currently seem worth the implementation effort to split up the code
path.

Fixes #22700

Disable flaky test WorkCoordinatorTests.FileFromSameProjectTogetherTest

See #25931

* Overload Resolution now fails with the correct error

* PR Comments

* Clean up

* Partial methods implementation should match declaration parameter ref kinds

* More tests

use latest language version for Miscellaneous Files workspace

Bind ForEachVariableStatementSyntax.Variables for error recovery

Make VBCSCompiler a non-critical process

* Previous PR comments

* Missing tests from test plan

* Enable unmanaged constraint on local functions

* Clean up

* PR Comments

* More tests

* PR Comments

This designation will allow Visual Studio to kill instances of
VBCSCompiler rather than showing it as blocking update installation.

closes #24610

Account for Mutex ctor throwing

InternalsVisibleTo for the completion test framework

Apply a hang mitigating timeout to WaitForLightBulbSessionAsync

* fixed bug where all documents are added as high priority on solution load.

* add tests

Fixed formatting for 'Use pattern matching code fix'

This changes the compiler server to be resilient in the face of the
Mutex constructor throwing an exception. It's documented as being able
to throw various exceptions but we never accounted for it. Had a real
world case pop up when using certain Docker containers on Linux.

In the case the Mutex ctor throws an exception just fall back to normal
csc / vbc execution. The build will complete just fine here, it just
won't have the performance boost of the compiler server.

closes #24124

Misc infrastructure fixes

* add more info on log

* put more data

Improve diagnostics when tests fail due to an asynchronous operation timeout

The space for archiving dump files is limited in Jenkins. Changing our
time out code to avoid creating dump files that won't be meaningful to
bug investigations.

closes #25793

Added IDiscardOperation to the IOperation API

Fix loc issue on "Manage Specifications" and "Manage styles" dialogs

Increase the UseExportProviderAttribute cleanup timeout to 1 minute