Relocation of backend4 projects to nfs-fileX fleet

The remaining 32TB of project data on the single legacy backend4 system needs to be distributed between the new NFS sharded fleet. This will reduce the 'hot-spot' that we have of roughly 70% of GitLab projects are still on a single NFS server.

/cc @pcarranza @jnijhof @ahanselka @stanhu