Geo: Don't retry repositories or files until everything has been backfilled

What does this MR do?

Skips file and repository retries until every file and repository has an entry in the Geo registry

Why was this MR needed?

Without this, initial backfill - which only needs to happen once - can be held up by repeatedly failing repositories or files. If a single repo or file is missing on the primary, and it takes 500,000 loops to complete backfill, then that missing item can be scheduled 500,000 times.

With this change, no matter how many loops it takes, each item will be scheduled once only in initial backfill. Once initial backfil is complete, retries will be scheduled as usual.

The log cursor directly schedules repository syncs in response to events from the primary now, so this shouldn't affect keeping frequently-updated projects up to date while the backfill is running.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

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

What are the relevant issue numbers?

Closes #3810 (closed)