Deduplicate choice of horizon for a relation procarray.c.
5a1e1d83022 was a minimal bug fix for
dc7420c2c92. To avoid future bugs of
that kind, deduplicate the choice of a relation's horizon into a new helper,
GlobalVisHorizonKindForRel().
As the code in question was only introduced in
dc7420c2c92 it seems worth
backpatching this change as well, otherwise 14 will look different from all
other branches.
A different approach to this was suggested by Matthias van de Meent.
Author: Andres Freund
Discussion: https://postgr.es/m/
20210621122919.2qhu3pfugxxp3cji@alap3.anarazel.de
Backpatch: 14, like
5a1e1d83022