Services in unopened projects

Some language services, such as `findAllReferences`, `rename`, `navigateTo`, and `getEditsForFileRename`, as well as refactors like `moveToNewFile` (which wants to update imports from external references), work best when they know about as many files as possible. Currently we only keep projects open if at least one file is being viewed in the editor. When we invoke a service that might need to know about unopened projects, we might consider walking up ancestor directories to look for a base `tsconfig.json` that references many projects, and opening those.