Fix up support for changing rule set files through the Solution Explorer 

* Fix naming, remove help button, let the UI has a default selected destination

* Add comments

* remote question mark from warning dialog

Merge dev16.0-preview3 to master

Remove unnecessary test hooks

Disable integration tests with <95% reliability

Bail out for error types from IDE0058 analyzer (unused expression value)

The AnalyzersCommandHandler was still trying to call GetHostProject
to find the host project as a way to directly grab the rule set file
to process that. That was deprecated but we hadn't fixed it up yet.

The fix is to re-thread through a way to get to the rule set. The
"ownership" of a rule set file (if one exists for a project) is owned
by the VisualStudioProjectOptionsProcessor, so we now need a way to jump
to that directly from any project so another map is added to the
VisualStudioWorkspaceImpl. That map is unfortunate -- the
OptionsProcessor is really something that should be private to the
project system itself and shouldn't be grabbable by any random code.

Fixes https://devdiv.visualstudio.com/DevDiv/_workitems/edit/779916
Completes task https://devdiv.visualstudio.com/DevDiv/_workitems/edit/698029

* Enable LinkedFileDiffMergingEditorTests.TestCodeActionPreviewAndApply test

* Enable InteractivePasteCommandhandlerTests.PasteCommandWithOutInteractiveFormat test

* Updated LinkedFileDiffMergingEditorTests with PR feedback
Co-Authored-By: NJoeRobich <joseph.robichaud@microsoft.com>

Support running integration tests in VS 2019

Handle null reference exception during analyzer execution when cancel…

Merge dev16.0-preview3 to master

These tests have an overall pass rate of 84% and 65%, respectively, over
the path 14 days.

See #30544

This test has an overall pass rate of 65% over the past 14 days.

See #33103

Ensure we refresh the project output path when the obj path changes

Fixes #33073

Add IterationDataAttribute for easy test looping

when it happens we will show the info bar and proceed. this is not error recovery but not forcing users to restart VS right away by crashing VS. now user will have time to do what they want and then restart VS

Disable ngen for System.Numerics.Vectors

Updated NuGet package properties

Make the flow analysis based unused value/parameters analyzer more conservative

don't retain fault result in task center if nuget info download failed.

Classify keywords in ForEachVariableStatements as ControlKeywords

If a solution is closed and reopened, still recreate a SolutionId

Fixes VSO Watson [#763828](https://devdiv.visualstudio.com/DevDiv/_workitems/edit/763828)
All the dumps for the watson show that cancellation was requested during analysis, leading to one thread clearing state while other thread faulted.

Do not report unused expression value (IDE0058) for expression body

Work around bug in NamedPipeClientStream.ConnectAsync

Updated version to 3.0.0 beta 4