Switch the error list scope combo box to match the newly selected background analysis scope in Tools Options.

Address PM feedback and change the user facing resource strings to match the error list terms in its scope filter combo box

`Active file` -> `Current Document`
`Open files and projects -> `Open Documents and Projects`
`Full Solution` -> `Entire Solution`

Revert an unnecessary change - we already handle the bail out for non-active files for active file analysis scope further in the code path

Revert the change to DesignerAttributeIncrementalAnalyzer to bail out for active file analysis scope.

Replaces the existing "Full Solution Analysis" option, with a background analysis scope to allow users to control the analysis scope for all solution crawler based background analysis.

Fixes #38429. Active file scope minimizes all the background analysis to the active files, saving on CPU consumption from background analysis on remaining files in the solution.

I have also updated up the low virtual memory listener which detects low VM and used to turn off just the full solution analysis to now set the background analysis scope to "Active file" for the current session.

Fixes #39564

Merge release/dev16.4 to master

Cleaning up the documentation on our compiler toolset packages to make
the supported use cases explicitly clear. Previously this information
was only avaliable in scattered issues throughout the repsitory
([example](https://github.com/dotnet/roslyn/issues/38312)).

The package description is likely the best place for this information.

- Control flow graph builder
- Using decl Ioperation tests
- PublicAPI.Unshipped.txt

Related to #39641.
Related to #39643.

Skip failing integration tests

Hook up "Run Code Analysis" commands in Visual Studio to execute Rosl…

This change also separates implementation of ISymbol interfaces from internal symbols in C# compiler.

Local function flow analysis has always been special-cased for definite
assignment, and specifically for definite assignment with monotonic
assignment. This change implements the same non-monotonic tracking that
we use for try-finally for local functions. This is a conservative
analysis, meaning that certain rare cases may not transfer as much
information as possible. It's currently assumed that these cases are
rare enough to not be frustrating. No safety problems should be present
in the conservative analysis.

Fixes #14400
Fixes #14214

Don't MEF import core Roslyn language service type in SolutionExplore…

Subscribe to OnModuleInstanceLoad/OnModuleInstanceUnload events only when managed debugging is being used. (#39568)

Avoids loading Roslyn when debugging native code only.

Introduce IUsingDeclarationOperation

* Remove project type from Bing URI

* Add Language to DiagnosticData

* Trim arguments that are too long

Make IUsingDeclarationOperation explicit, and the underlying IVariableDeclarationGroupOperation implicit.

Merge release/dev16.4 to master