Use libpq for connection testing in pg_regress

When Who What
2023-10-25 08:17:15 Daniel Gustafsson (d_gustafsson) Closed in commitfest 2023-11 with status: Committed
2023-10-25 08:17:15 Daniel Gustafsson (d_gustafsson) Changed committer to d_gustafsson
2023-10-02 10:01:53 Peter Eisentraut (petere) Closed in commitfest 2023-09 with status: Moved to next CF
2023-08-29 12:44:44 Daniel Gustafsson (d_gustafsson) Changed authors to Daniel Gustafsson (d_gustafsson)
2023-08-29 12:44:36 Daniel Gustafsson (d_gustafsson) Attached mail thread 20230808021541.7lbzdefvma7qmn3w@awork3.anarazel.de
2023-08-29 12:44:36 Daniel Gustafsson (d_gustafsson) Created patch record