mgr/volumes: Deprecate protect/unprotect CLI calls for subvolume snapshots

mgr/volumes: Deprecate protect/unprotect CLI calls for subvolume snapshots

Subvolume snapshots required to be protected, prior to cloning the same.

Also, protected snapshots were not allowed to be unprotected or removed,
if there were in-flight clones, whose source was the snapshot being
removed.

The protection of snapshots explicitly is not required, as these can be
prevented from being removed based only on the in-flight clones checks.

This commit hence deprecates the additional protect/unprotect requirements
prior to cloning a snapshot.

In addition to deprecating the above, support to query a subvolume for
supported features, via the info command, is added. The feature list
is set to "clone" and "auto-protect", where the latter is useful to
decide if protect/unprotect commands are required or not.

Fixes: https://tracker.ceph.com/issues/45371
Signed-off-by: Shyamsundar Ranganathan <srangana@redhat.com>
(cherry picked from commit c52a7383d391864b7dce3ba09197a077a998dff7)

Conflicts:
        doc/cephfs/fs-volumes.rst
- added line space for correcting multi-line command rendering