Add relallfrozen to pg_class

Add relallfrozen to pg_class

Add relallfrozen, an estimate of the number of pages marked all-frozen
in the visibility map.

pg_class already has relallvisible, an estimate of the number of pages
in the relation marked all-visible in the visibility map. This is used
primarily for planning.

relallfrozen, together with relallvisible, is useful for estimating the
outstanding number of all-visible but not all-frozen pages in the
relation for the purposes of scheduling manual VACUUMs and tuning vacuum
freeze parameters.

A future commit will use relallfrozen to trigger more frequent vacuums
on insert-focused workloads with significant volume of frozen data.

Bump catalog version

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Nathan Bossart <nathandbossart@gmail.com>
Reviewed-by: Robert Treat <rob@xzilla.net>
Reviewed-by: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Greg Sabino Mullane <htamfids@gmail.com>
Discussion: https://postgr.es/m/flat/CAAKRu_aj-P7YyBz_cPNwztz6ohP%2BvWis%3Diz3YcomkB3NpYA--w%40mail.gmail.com