mds: collapse numerous client warnings into one

...to avoid sending O(N_clients) sized beacons.

Fixes: #9375

Signed-off-by: John Spray <john.spray@redhat.com>
messages: add cephfs client metadata to MClientSession

Signed-off-by: John Spray <john.spray@redhat.com>
mds: store client metadata on Session

Signed-off-by: John Spray <john.spray@redhat.com>
mds: include client metadata in `session ls`

Signed-off-by: John Spray <john.spray@redhat.com>
ceph_fuse: refactor init to make mount_point accessible

...so that we can read out the mount point between init
and start() in order to feed it to Client before it connects
to the MDS.

Signed-off-by: John Spray <john.spray@redhat.com>
client: send metadata in session open

Populated with hostname and entity_id by
default, with interface for outer layers
like ceph_fuse, libcephfs to inject their
own metadata.

Signed-off-by: John Spray <john.spray@redhat.com>
ceph_fuse: include mount point in client metadata

Signed-off-by: John Spray <john.spray@redhat.com>
mds: generate friendly name for client sessions

...from the client metadata, for use in health messages.

Signed-off-by: John Spray <john.spray@redhat.com>
mds: implement const SessionMap::get_session

Signed-off-by: John Spray <john.spray@redhat.com>
mds: use new Session::human_name in health msgs

Signed-off-by: John Spray <john.spray@redhat.com>