mgr/orch: service ls -> ps, add DaemonDescription

mgr/orch: service ls -> ps, add DaemonDescription

- We keep ServiceDescription around unmodified (although it will need some
  cleanup later)
- We add DaemonDescription, and clean out the service-related ambiguities
- Add a new list_daemons() method for Orchestrator
- Add a new 'ceph orch ps' command
- In cephadm, drop get_services(), and implement list_daemons()
  - a million changes to make this work
- Adjust health alert and option names

Signed-off-by: Sage Weil <sage@redhat.com>