Fix debugger visualizer

VS crash during EnC around active statements

Fix #3894.

Make MethodBody.IL immutable

Clean up Interactive vsixes...

Fix #3894. Note that VB porting will be followed.

Several refactorings to rework the internal Completion List API

Remove unused field and methods from tagging infrastructure.

This is willfuilly inconsistent with the methods in CodeFixProvider, CodeRefactoringProvider
and DiagnosticAnalyzer becuase the name feels a bit better in this case. This might be changed
following an API design review before being made public.

This is preliminary work for Interactive setup authoring.

- Fix versions of InteractiveWindow and VsInteractiveWindow at 1.0.0.0 so
  as not to break existing consumers (e.g. Python Tools).
- Redirect consumers of the VsInteractiveWindow to 42.42.42.42 in the
  RoslynDev hive.
- Delete some unused Debugger stuff from VisualStudioInteractiveServices.
- RootNamespace and AssemblyName should match TargetVsixContainerName to
  avoid confusion.
- Don't deploy an extra copy of Microsoft.CodeAnalysis.VisualBasic.dll
  with Roslyn.VisualStudio.Setup.Interactive.vsix.

Spelling corrections in C-Sharp compiler

Conflicts:
	src/Compilers/Test/Resources/Core/CompilerTestResources.csproj
	src/Compilers/Test/Resources/Core/ResourceLoader.cs
	src/Compilers/Test/Resources/Core/TestResources.cs

Rename BlobWriter to BlobBuilder

Make CompilerTestResources portable

* Convert the ICompletionProvider interface to a CompletionListProvider abstract class.
* Rename CompletionItemGroup to CompletionList
* Introduce a CompletionListContext type to be used by providers to specify the contents and
  details of CompletionLists with a RegisterCompletionListAsync() method.
* Change GetGroupsAsync() method to GetCompletionListAsync(), which returns Task<CompletionList> rather
  than Task<IEnumerable<CompletionList>>.
* Move code that merges, de-dupes and sorts completion lists from the controller into the
  completion service. This affected a few VB spell check unit tests which now change their ordering
  slightly.

Move all InternalsVisibleTo into the project files

More MSBuildTask cleanup

Use nameof instead of hardcoded argument names.

Added a document that lists some CodeGen differences.

This moves all of the InternalsVisibleTo which were defined in code into
the project files where the majority of the IVT definitions lived.