mgr/nfs: Add support for RGW export
Current interface for CephFS:
The "ceph nfs cluster create" command also accepts a "type" argument which may be "cephfs" or "rgw". Currently only "cephfs" is supported. This ticket is for adding rgw support.
Most of the work for this ticket is setting up the appropriate NFS-Ganesha configuration for rgw exports. There is a nice ASCII art diagram of the configuration distribution here: https://tracker.ceph.com/issues/47490