Currently, we don't let users enable dags.gitSync and dags.persistence at the same time.

If we do this (obviously requiring dags.persistence.accessMode = ReadWriteMany), we can massively reduce the number of git-sync containers required.

This is because we won't have to put a git-sync container in every Pod, but rather have all pods mount the PVC, while having a central single git-sync deployment that keeps the PVC up to date.