WIP: Add logging to repository update workers

Closed Collen requested to merge add-logging-to-repository-update-workers into master

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.

/cc @MrChrisW @athar