* Permit selecting an instance from a type in a sub-expression in nameof(...)

Fixes #20600

Skipping PasteCommandWithOutInteractiveFormat test

Skipping TestSelection test

Skipping TestRegionCompletionCommitFormatting test

* first refactoring to add connection pool

* pool added

* removed usage of KeepAliveSession which solely used as performance benefit favoring perf over complexity.

now with pool, there is no perf advantage by KeepAliveSession. it should be only used when one wants to make connection stateful.

* change remote call signature since solution is now set automatically

* fixed test failures

* made some constant an options. and made pool off by default

handle pool shutdown better

* now turn it on by default

* PR feedbacks

* address more PR feedbacks

* more comments

* renamed ConnectionPool to ConnectionManager. people seems confused by name too much. pool is just one of thing it does, it owns connection management in general.

* PR feedbacks

* change Contract.Fail to Contract.Require so that it doesn't crash VS when OOP is killed explicitly by users.

* PR feedbacks

* address feedbacks

* put finalizer under debug flag

Fix running unit tests in MicroBuild

We were launching xunit by ShellExecute'ing not the procdump executable,
but rather the folder that contained the procdump executable. That
really doesn't work well, it turns out.

Fix CSharpFormattingOptions csharp_space_around_binary_operators key

Merge pull request #24173 from MaStr11/SuppressIDE0041_UseIsNullcheck_ForUnconstraintGenericParameters

Suppress 'IDE0041 Null check can be simplified' for unconstraint generic parameters.

GetHashCode code generator should produce code that doesn't overflow in checked mode.

Merge dev15.6.x to dev15.7.x

Do not suggest var when it change static type of the variable in foreach statement

Localization test failures 2

case 'type constraint': no fix offered
case 'reference constraint': C# use '==null' instead of  'is null'
default: C# 'is null', VB 'IsNothing'

Enable VerifyCodeRefactoringOffered tests

Enable ExtractViaCodeActionWithMoveLocal

Fixes issue #20355?

Is there something special about this bug or am I missing something? There's just an extra space that needs removed, right?

Enable xUnit xml output generation on microbuild

Produce warning for VB code.

Fix spelling mistake.

Add loc files.

Fall back to tuples if they're available when making a hashcode.

Use System.HashCode if its available.

Use 64bit math when computing VB hashcodes in checked contexts.

Use full 32 bits for vb hash.

Cleanup

Localization test failures 1

We need xml files to report results to MicroBuild. This is what our
build queue expects but must have been broken semi-recently.

Skipping ProjectionBuffersWork test

Skipping PasteCommandWithInteractiveFormatAsBoxCopy test

The underlying requirement that diagnostics be waitable through
FeatureAttribute.DiagnosticService was recently implemented (#24783),
so these tests should be reliable again.

Fixes #17393

Switch some .ConfigureAwait(true) to .ConfigureAwait(false)

* Ensure modreq must exist on PE symbols that C# compiler expects them to have

* PR feedback

* More tests + feedback

* Skip tests on mono due to bug

* Added Assert.True(IsOverride) for overrides