Add a lint check to restrict use of Rugged

What does this MR do?

Adds a lint check to the static-analysis CI job that prohibits use of Rugged outside lib/gitlab/git.

The job has a whitelist so we can make exceptions.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

We are replacing Rugged with Gitaly.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?