* Remove lots of duplicated code
* Add support for testing external code elements

Remove PumpingWait

This removes PumpingWait from our test infrastructure and replaces it with proper await calls on the Task(s) in question.

Add a PE file section for determinism

Fixes for Building with Update 1

Properly map snapshot points up when testing if adornments should be visible or not.

Fixes #5969

By luck, we were getting the real version we did want, but this is
correct.

These interfaces change between VS versions, so this makes us not
dependent upon a specific version of VS.

We don't need SolutionDir or RestorePackages, which were for very old-
style restore systems.

With Visual Studio 2015 Update 1 you should not specify -anycpu
in the runtimes section. Right now we'll have both to allow us to build
with and without Update 1, and we'll remove the old ones once we've
made the transition.

Update 1 also tries deploying implementations for some class libraries,
so I'm updating all our test and VSIX deployment class libraries to
now include implementations.

Update 1 defaults to copying implementations for some class libraries, but we
don't need that for our feature binaries.

Handle in-memory assemblies correctly in ScriptOptions.AddReference and when adding reference to the host object

Handle in-memory assemblies correctly in ScriptOptions.AddReference and when adding reference to the host object

Hide namespaces and types of the host assembly

Keep accessor  with attributes on a single line.

Fixes #4720

Don't add accessors for a property with an arrow-body

Port commit from PR #6194 to stabilization branch

Add a "deterministic end-to-end test" runner

[ask mode]Remove unwanted public APIs and enable public API analyzers for Interactive (Editor) Features

Implements recursive reference aliases

Public API changes recommended by the design team for the new Analyzer/Suppression APIs.
• CompilationWithAnalyzerOptions should be sealed
• CompilationWithAnalyzerOptions.AnalyzerOptions should be renamed Options
• SuppressionInfo should be sealed
• AnalyzerTelemetry API changes as per this comment.

There are no functionality changes here.

Fixes #6044

Explicitly invoke diagnostic re-analysis whenever any bulk suppression fix is invoked from the error list or solution explorer.

Fixes #6007

Propagate imports to synthesized methods

Fixes #2501