pybind/rbd: add Python bindings for mirror group control

pybind/rbd: add Python bindings for mirror group control

Add methods to the rbd.Group class for mirror group operations:
- mirror_group_enable(mode) / mirror_group_disable(force)
- mirror_group_promote(force) / mirror_group_demote()
- mirror_group_resync()
- mirror_group_get_global_status()
- mirror_group_get_instance_id()

Also adds the required Cython declarations in c_rbd.pxd for
rbd_mirror_group_status_state_t, rbd_mirror_group_site_status_t,
and rbd_mirror_group_global_status_t structs.

Fixes: https://tracker.ceph.com/issues/74707
Signed-off-by: Imran Imtiaz <imran.imtiaz@uk.ibm.com>