WIP: Fix forget and mark to-delete restic snapshots of deleted PVs
This MR includes:
- New cronjob for
cephfs-backup-forget-deleted-volumes
- Move tests from .gitlab-ci to tests/*
- Add tests to see if we delete restic repositories of deleted PVs
- Update doc to document restic repositories deletion for deleted PVs
- Fix TMPDIR to point to /root/.cache instead of /.cache