Status update for a commitfest entry.
This patch is ReadyForCommitter. It applies and passes the CI. There are no unanswered questions in the discussion.
The discussion started in 2015 with a patch by Jeff Janes. Later it was revived by Pavan Deolasee. After it was picked
upby Ibrar Ahmed and finally, it was rewritten by me, so I moved myself from reviewers to authors as well.
The latest version was reviewed and tested by Ibrar Ahmed. The patch doesn't affect COPY FREEZE performance and
significantlydecreases the time of the following VACUUM.