crimson/osd: manage PG_STATE_SNAPTRIM when trimming snaps

crimson/osd: manage PG_STATE_SNAPTRIM when trimming snaps

After a few tries:

```
$ bin/ceph -s
*** DEVELOPER MODE: setting PATH, PYTHONPATH and LD_LIBRARY_PATH ***
2022-12-19T20:18:21.856+0000 7ff87b46f700 -1 WARNING: all dangerous and experimental features are enabled.
2022-12-19T20:18:21.857+0000 7ff87b46f700  1 build_initial for_mkfs: 0
2022-12-19T20:18:21.860+0000 7ff87b46f700 -1 WARNING: all dangerous and experimental features are enabled.
2022-12-19T20:18:21.861+0000 7ff87b46f700  1 build_initial for_mkfs: 0
  cluster:
    id:     347aedc9-d72f-4a34-98fc-26cb04b0c2fc
    health: HEALTH_WARN
            11 mgr modules have failed dependencies
            1 pool(s) do not have an application enabled
            1 pool(s) have no replicas configured

  services:
    mon: 1 daemons, quorum a (age 3m)
    mgr: x(active, since 3m)
    osd: 1 osds: 1 up (since 3m), 1 in (since 3m)

  data:
    pools:   1 pools, 1 pgs
    objects: 95 objects, 6 B
    usage:   1.0 GiB used, 100 GiB / 101 GiB avail
    pgs:     1 active+clean+snaptrim

  io:
    client:   1.2 KiB/s wr, 0 op/s rd, 1 op/s wr
```

Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>