Project selection should incorporate whether or not a project is "valid"

[thecrypticace]

See #1406 (comment)

The idea here is that during project matching, if possible, we should check to see if the project is valid and skip projects that are not. Now this is a bit complicated because projects are initialized lazily but I think we can change project selection behavior if a project is initialized and detected to have an invalid config or CSS or something.

Additionally, we should capture and surface errors parsing CSS files for v4 so they can be displayed right in the editor. The errors don't surface source location information currently so they should be pinned to 0:0 in the CSS file. Once we start throwing errors with source location information IntelliSense can more intelligently place the errors.