[Review Only] JS Code Hints: Remember timed out files, notify user

@dangoor 

I pushed this interim branch for you to take a look. This works for some code paths.

TODO:
- [ ] bug: `isFileExcludedInternal()` not called on all code paths
- [ ] implement, invoke notification dialog
- [ ] convert pref to project scope?
- [ ] remove `console.log()` statements
- [ ] rebase this branch