ReplicatedPG,rados: add CEPH_OSD_[COPY_FROM]_SNAPID_CLONE for promote

Otherwise, we don't have a way to distinguish between client requests where we
should return -ENOENT if the snapid is removed and promotion requests where we
should interpret the snapid as a clone id directly.

Fixes: #7858
Signed-off-by: Samuel Just <sam.just@inktank.com>
Merge remote-tracking branch 'origin/wip-7858' into wip-sam-testing