tools/cephfs_mirror: Add per-peer tick thread with configurable interval
Introduce a per-peer tick thread controlled by cephfs_mirror_tick_interval
(default 5 seconds). The interval is re-read each iteration so configuration
changes take effect without restarting the daemon. The thread provides a
generic hook for future periodic mirroring work.
Fixes: https://tracker.ceph.com/issues/76686
Signed-off-by: Kotresh HR <khiremat@redhat.com>
(cherry picked from commit
b8310f33c377b4c3e3f43026184f5fdd741f6a8e)