Geo: Reduce frequency of redownload attempts

What does this MR do and why?

• Instead of only attempting to retry syncs with the "redownload" flow after the threshold is reached, now we alternate between the "normal" and "redownload" flow for each retry
• Increase the threshold for using the "redownload" flow from 5 to 10 retries

This increases the resilience of retries because:

1. Sometimes "redownload" doesn't work but a "normal" sync does: #324208 (closed)
2. The "redownload" logic is not totally compatible with Gitaly Cluster: #332151 (closed)

How to set up and validate locally

For example to test project resync:

1. Checkout this branch in your secondary GDK/gitlab repo
2. In Rails console, do registry = Geo::ProjectRegistry.first
3. registry.update!(repository_retry_count: 7, resync_repository: true)
4. In another tab: tail -f log/geo.log
5. Resync the project Git repo: Geo::RepositorySyncService.new(registry.project).execute
6. Notice that Redownloading repository is not output (whereas it is output without this change)

Similar can be done to test different retry counts, or project-wikis, or designs, or snippets, or group wikis.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.