Add callbacks for fixed-numbered stats flush in pgstats

When Who What
2024-09-09 02:16:09 Michael Paquier (michael-kun) Closed in commitfest 2024-11 with status: Committed
2024-09-09 02:16:09 Michael Paquier (michael-kun) Changed committer to michael-kun
2024-09-03 04:50:04 Michael Paquier (michael-kun) Changed authors to Michael Paquier (michael-kun)
2024-09-03 04:50:04 Michael Paquier (michael-kun) Changed targetversion to 18
2024-09-03 04:49:48 Michael Paquier (michael-kun) Attached mail thread ZtaVO0N-aTwiAk3w@paquier.xyz
2024-09-03 04:49:48 Michael Paquier (michael-kun) Created patch record