Installing Flutter extension with a project open results in a prompt saying to install Flutter extension #1755

If you have a Flutter project open, but don't have either extenstion installed, then installed Flutter from the marketplace, you see this:

This is because the Dart extension installs first (it's a dependency) and activates (because of the open project), and notices you don't have Flutter installed. We should delay this prompt and re-query after a short while. We may even wish to do a silent-restart if the Flutter extension is installed after Dart has already activated.