Update background migration populating Draft column

There were enough failed jobs in the background migration that originally populated the draft column (!63703 (merged)) to warrant a 2nd, follow-up migration that essentially duplicates the original migration, but with a smaller batch size and with the newly added job completion tracking enabled. (!66788 (comment 635792082))

First, however, we need to cleanup data that was incorrectly populated with a leaky SQL regex - #356220 (closed)