Consider how GitHub private code tooltip evolves with Cloud supporting private repos

Created by: quinnkeast

When a user on GitHub has the browser extension installed and is on a private repo, but doesn't have a valid Sourcegraph URL, they're given this tooltip:

Once Cloud supports private repos for users, the scenario changes a bit.

• Users might have the extension pointing at Cloud
• Users might:
  • Not have any code host connections on Cloud
  • Not have any private repos on Cloud
  • Not have the related private repo on Cloud

We'll need to evolve this tooltip once private code is GA.