Don't consume the response file when re-initializing after ```#reset
noconfig```.  The host already handles this correctly.

Fixes #4397.

Integration test to follow.

Fix Add using under chained conditional access expressions.

Implement missing LangVersion checks for new features/relaxations introduced in VB14.

Minor SourceFileResolver fixups...

Fixed code styles and added one more test.

Fixes #5072.
Also fixed some issues around LangVersion handling, which were found along the way.

Swallow ArgumentOutOfRangeException while retrieving custom debug info

Disable snippets in the Interactive window

- Undo some refactoring of CommonCompiler.ReadFileContent
- Remove LoadDirectiveResolver
- Make SourceReferenceResolver.ReadText detect encoding
- Make SourceReferenceResolver.ReadText Dispose its Stream
- Generate Diagnostic if source contains #load and SourceReferenceResolver
  is not specified in ParseOptions

Use async read for process output

Fix crash in VerifyForwardedTypes

Add a new analyzer and code-fix to detect and recommend when people can use the auto-property pattern.

Add a semaphore to NuGet and Mono restore

Change unzip to use the -u option instead of the -f option

Add more filters

The -f option doesn't include files that don't already exist, while the
-u option updates existing files and also adds files that don't exist.

Also, we were deleting the zip file after unzipping, leading the caching
to always fail and download new zip files every time, so this should
allow caching to work again.

Sometimes the debugger returns the HRESULT for
```ArgumentOutOfRangeException```, rather than ```E_FAIL```, for methods
without custom debug info (https://github.com/dotnet/roslyn/issues/4138).

After calling nextHandler(), backspace completion should verify that …

Persist Interactive window visibility across VS restarts

Right now we parallelize by sticking multiple mac builds on the same machine. Since NuGet and Mono toolset restores are machine-global, sometimes the builds stomp on one another. This adds a semaphore to only allow one build to restore at a time.

Calculate snippet $end$ location based on column, not line length

...for v1.  Filed #5107 to revive them.

(There are fewer VB tests since VB doesn't have SurroundWith and
Interactive window completion is NYI.)

Bonus: Improve consistency between ```ExecuteCommand``` and
```GetCommandState``` in snippet handler.

Fix downgrade warnings in NuGet restore