mgr, mon: Keep upto date metadata with mgr for MONs

mgr, mon: Keep upto date metadata with mgr for MONs

The mgr updates mon metadata through handle_mon_map which
gets triggered when MONs were removed/added from/to cluster or
the active mgr is restarted or mgr failsover.
We could have handled metadata update through MMgrOpen or
early MMgrReport messages but these are sent before monitor
electin completes and lead monitor updates pending metadata
in monstore. Instead of relying on fetching mon metadata using
'ceph mon metadata <id>' command, explicitly send metadata
update request with mon metadata to mgr.

Fixes: https://tracker.ceph.com/issues/55088
Signed-off-by: Prashant D <pdhange@redhat.com>
(cherry picked from commit 1a065043b964f8c014ebb5bc890a243c398ff07c)