What does this MR do?
Adds error logging for failed pull from and push to a remote repository to RepositoryUpdateRemoteMirrorWorker and RepositoryUpdateMirrorWorker.
Why was this MR needed?
Users are only notified via the UI at
/settings/repository. It's helpful if this is captured in the logs as well, as requested by this customer: https://gitlab.zendesk.com/agent/tickets/78180.