repo-updater: Add PermsSyncer to syncer & sync private repo perms
Created by: indradhanush
Follow up on #23884.
In this commit we trigger a repo permissions sync for all private repos (both added and modified) in the diff read from the syncer.Synced channel. We do not make extra checks for existing private repos that were modified as we do not anticipate a performance based regression based on the number of repos being scheduled for permissions syncing.
Post merge
When this is out on dotcom, I will keep an eye on the Permissions dashboard, specifically:
Repo permissions synced per minuteRepo permissions sync durationRepo permissions sync error rate