ReplicatedPG: handle FLAG_OMAP on promote and copyfrom

Fixes: #7967
Signed-off-by: Samuel Just <sam.just@inktank.com>
osd/: track num_objects_omap in pg stats

Fixes: #7831
Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG::agent_choose_mode: exclude omap objects for ec base pool

Fixes: #7831
Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG::agent_choose_mode: use num_user_objects for target_max_bytes calc

Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG::agent_choose_mode: improve debugging

Signed-off-by: Samuel Just <sam.just@inktank.com>
ReplicatedPG::_delete_oid: adjust num_object_clones

Signed-off-by: Samuel Just <sam.just@inktank.com>
Merge pull request #1614 from ceph/wip-7964

Wip 7964

Reviewed-by: Sage Weil <sage@inktank.com>