mgr: enhance the rados service

mgr: enhance the rados service

For some use cases, like the tcmu-runner, there maybe handreds or
thousands of LUNs, and then for each LUN it will register one service
daemon, then in the `ceph -s` output will be full of useless info.

This will allow to classify the sevices service daemons in one
specified format by adding two pairs in metadata:

  "daemon_type"   : "${TYPE}"
  "daemon_prefix" : "${PREFIX}"

TYPE: will be used to replace the default "daemon(s)"
showed in `ceph -s`. If absent, the "daemon" will be used.
PREFIX: if present the active members will be classified
by the prefix instead of "daemon_name".

For exmaple for iscsi gateways, it will be something likes:
  "daemon_type"   : "portal"
  "daemon_prefix" : "gw${N}"

Then the `ceph -s` output will be:

  ...
  services:
    mon:   3 daemons, quorum a,b,c (age 50m)
    mgr:   x(active, since 49m)
    mds:   a:1 {0=c=up:active} 2 up:standby
    osd:   3 osds: 3 up (since 49m), 3 in (since 49m)
    iscsi: 8 portals active (gw0, gw1, gw2, gw3, gw4, gw5, gw6, gw7)
  ...

Fixes: https://tracker.ceph.com/issues/49057
Signed-off-by: Xiubo Li <xiubli@redhat.com>