mgr/orchestrator: drop $realm.$zone naming convention

mgr/orchestrator: drop $realm.$zone naming convention

- Let users name the rgw service(s) whatever they like
- Make the rgw_zone and rgw_realm arguments optional, so that they can
  omit them and let radosgw start up in the generic single-cluster
  configuration (whichk, notably, has no realm).
- Continue to set the rgw_realm and rgw_zone options for the daemon(s),
  but only when those values are specified.
- Adjust the CLI accordingly.  Drop the subcluster argument, which was
  only used to generate a service_id.
- Adjust rook. This is actually a simplification and improved mapping onto
  the rook CRD, *except* that for octopus we enforced the realm.zone
  naming *and* realm==zone.  I doubt a single user actually did this
  so it is not be worth dealing with, but we need a special case for
  where there is a . in the service name.

Signed-off-by: Sage Weil <sage@newdream.net>
(cherry picked from commit af0216d93fb522d239b10b5d7d18208ee02fed77)

# Conflicts:
#	src/pybind/mgr/rook/rook_cluster.py
  - pacific branch does not have type annotation on apply_objectstore()