Fix CI issues after Github Actions networking changes (#7624)

For some reason using localhost in our hba file doesn't have the
intended effect anymore in our Github Actions runners. Probably because
of some networking change (IPv6 maybe) or some change in the
`/etc/hosts` file.

Replacing localhost with the equivalent loopback IPv4 and IPv6 addresses
resolved this issue.

(cherry picked from commit 8c9de08)

src/test/regress/pg_regress_multi.pl

@@ -297,10 +297,12 @@ sub generate_hba
 
  open(my $fh, ">", catfile($TMP_CHECKDIR, $nodename, "data", "pg_hba.conf"))
  or die "could not open pg_hba.conf";
- print $fh "host all alice,bob localhost md5\n";
+ print $fh "host all alice,bob 127.0.0.1/32 md5\n";
+ print $fh "host all alice,bob ::1/128 md5\n";
  print $fh "host all all 127.0.0.1/32 trust\n";
  print $fh "host all all ::1/128 trust\n";
- print $fh "host replication postgres localhost trust\n";
+ print $fh "host replication postgres 127.0.0.1/32 trust\n";
+ print $fh "host replication postgres ::1/128 trust\n";
  close $fh;
 }