Don't offer several code actions on identifiers that are likely intended to be C# keywords.

Add more scenarios to CSharpCodeActions

Outlining VSI tests

Fixes #18311 - Incorrect quick info for ValueTuple<T>

Use the project display name in FAR to support grouping

Update IDE Test Plan.md

Port the rename integration tests to the new framework.

Port the Formatting tests to the new framework

Don't create deferred projects for things that opt-out of DPL

Port Generate From Usage tests

Port go to implementation tests

Some NuGet targets also use this property and they expect a trailing
slash to be present

While investigating #17570, I discovered that we would sometimes create
"deferred" Roslyn projects for .NET Core projects that just hadn't been
asynchronously created yet. In *theory* that did no functional harm - they would
just get closed and converted to real projects when the project system created
the real project, but might as well not even bother creating them.

While I'm here, clean up PR feedback from #17335.

Also, update ProjectDisplayName to do what the docs say it does for Venus files.

Partially addresses #18382.