Step 1: Add HostProject
This is a somewhat complex addition to the ProjectSnapshotManager. Now
that we accept updates from the underlying IDE project system we need to
coordinate those with the Workspace.
This means that ProjectSnapshot itself now also has a version concept.
Step 2: Introduce a new project system based on CPS
We use project capabilities defined by the Razor SDK to determine
whether to rely on MSBuild evaluation to detect the configuration or
whether to fallback to assembly-based detection.
Step 3: Flow RazorConfiguration everywhere
We use now expose the RazorConfiguration to the language service and
editor. This means that we no longer need to detect the project's
configuration asynchronously, it happens much faster now.
This change adds an actual background worker for listening to project
change notifications and starts sending updates when the project's razor
dependencies change.
I had to do a litle surgery to get things working. There were plenty of
small bug fixes.
Additionally I got rid of the WeakReferences for tracking listeners. I
was seeing TextBuffers hanging around in VS longer than I expected and
the WeakReferences weren't getting cleaned up. I think it's better that
we just track the lifetime.