Geo - Fix repository synchronization order for projects updated recently

What does this MR do?

Take the last_repository_successful_sync_at column into account when ordering the projects updated recently.

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

Should we also take last_wiki_successful_sync_at into account?

Why was this MR needed?

We are prioritizing repositories with high activity, so repositories that the last sync failed but never received an update will be picked later or never.

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
• If paid feature, have we considered GitLab.com plan and how it works for groups and is there a design for promoting it to users who aren't on the correct plan
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/5054