osd,crimson/osd: use pg_committed_to rather than mlcod for submit_transaction

osd,crimson/osd: use pg_committed_to rather than mlcod for submit_transaction

This commit actually changes the bound we're propagating.  This solves
two bugs:
- Using min_last_complete_ondisk caused replicas to be two update rounds
  behind rather than one
- Replicas don't actually have enough information to set
  min_last_complete_ondisk on activation, so we couldn't serve replica
  reads until the first write.  pg_committed_to, on the other hand, is
  fine as the activation last_update cannot become divergent.

Moreover, last_complete won't advance past missing objects causing
min_last_complete_ondisk to be blocked by any replica missing object.
Note that the replica read pathway seperately checks whether the target
is missing locally, so that property was not needed.

Fixes: https://tracker.ceph.com/issues/65086
Fixes: https://tracker.ceph.com/issues/65085
Signed-off-by: Samuel Just <sjust@redhat.com>