[CBM] Investigate whether restore should skip purged deletes

What's the issue?
Now that we've fixed MB-47653, we have the issue that we maintain tombstones during a merge; this will result in tombstones being created on the target cluster during a restore (this may not be desirable).

What's the fix?
We should investigate whether we should skip restoring tombstones which are behind the purge seqno (in a similar fashion to the previous behavior with merge).