Improve Geo repository sync performance for larger databases

What does this MR do?

Replaces a SELECT id FROM projects WHERE id NOT IN (up to 1.5 million IDs) clause in a query with something that scales better with a large number of projects.

This is still terrible and should be replaced with postgres_fdw as soon as possible.

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

Why was this MR needed?

Geo testbed reliably errors out on this query

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
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #3269 (closed)