We wouldn't correctly handle the lazy tab case otherwise.

AbstractProject had two properties: Workspace and VisualStudioWorkspace
which was very, very confusing. We reduce down to one, and the few
places that needed the derived types

Our previous heuristic is we tracked any document that had a moniker
that wasn't contained within any project in VisualStudioWorkspace.
This was implemented with a private hook between the two systems. This
blows up in the face of other parties wishing to create their own
workspaces against files in the RDT, since we stomp on them. The new
heuristic is we attach to any file that's open and doesn't already have
a workspace, and we watch for registration changes to back off if
something else has taken a file.

Fixes #8598.

 fix issue 8315

Update NuGet to 3.4.0.645 and remove ZIP usage on WIndows

Provide a service to resolve an assembly name in a project context to an actual dll path.

Provide a way for 'code action' tests to pass data to their CodeFixProvider constructor.

Add support for merging preview items across multiple operations.

Provide a way for code actions to supress diagnostics in their previews.

Remove unnecessary casts.

Note: we now need to Explicitly reference 'MetadataReader' in 'System'.

This is necessary because a new reference to MS.VS.Shell.Design has a
namespace called 'Metadata', and have to now disambiguate these two names.

This is useful for code actions that will make changes that can't be
represented in the Roslyn snapshot model.  Because of this, the
preview may end up showing errors that teh code fix doesn't want to
be shown (because after the code fix actually applies, no error will
occur).

This is useful for testing purposes so we can pass mocks to the
specific CodeFixProvider constructor.  For example 'add nuget reference'
will pass mocks for the nuget search and install services in its tests.

Also provide a way for code action operations to state if they should
be invoked during tests.  Lots of tests just want to examine the
state returned by certain operations (like SolutionChangedOperation).
However, for mutating operations, some tests need the operation to
actually apply so that they can check the results of the operation.

Silence "No source files" build warning

Also, wrap all code action operations with an undo transaction.
This way we will attempt to undo all changes as one user undo
action.

CSharpAnalyzers.Vsix.vbproj was pulling CSharp targets and csc.exe, so their supressed warnings were not being respected.
Suppressed this warning in CSharpAnalyzers.Vsix.csproj.

This prevents the VS and the repository's version of NuGet
fighting over the format of project.lock.json.

NuGet restore is significantly faster with NuGet 3.4.0.645
than it has been in previous versions. We now always
restore on Windows PR builds.

This reduces package restore on Roslyn.sln with all packages already restored from 40 seconds -> 10 seconds.

project.lock.json format has changed since we last updated.

 Asynchronously produce the SpellChecker used for fuzzy matching.

Remove EventListener crash workaround

We've turned off AppDomain isolation in https://github.com/dotnet/roslyn/pull/8672 and https://github.com/dotnet/roslyn/pull/8534.

Merge stabilization into master

Use common output directory for Samples.

[Ask Mode] Fix IOperation crash caused by passing null for ConstantValue when creating Lite…

Search projects in parallel.  Cancel any parallel work once enough results are found.

Ask Mode request: Prevent DeriveArgument from throwing ArrayIndexOutOfRangeException when presented with semantically malformed bound trees.

Prevent DeriveArgument methods from trying to access parameter symbols that don't exist.

Disable DocCommentTest Include_Cycle_WRN_XMLDocInvalidXMLFragment

This time it is caused by BontrolVariable bounf to BoundBadExpression.
Also improved the robustness in the Condition property.

EnC: Fix handling ByRef parameters in anonymous delegates

Fix reset interactive build cancellation

Do not offer to create p2p references if the project system will not allow those references.