pgsql: BRIN: be more strict about required support procs

BRIN: be more strict about required support procs

With improperly defined operator classes, it's possible to get a
Postgres crash because we'd try to invoke a procedure that doesn't
exist. This is because the code is being a bit too trusting that the
opclass is correctly defined. Add some ereport(ERROR)s for cases where
mandatory support procedures are not defined, transforming the crashes
into errors.

The particular case that was reported is an incomplete opclass in
PostGIS.

Backpatch all the way down to 13.

Reported-by: Tobias Wendorff <tobias(dot)wendorff(at)tu-dortmund(dot)de>
Diagnosed-by: David Rowley <dgrowleyml(at)gmail(dot)com>
Reviewed-by: Tomas Vondra <tomas(at)vondra(dot)me>
Discussion: https://postgr.es/m/fb6d9a35-6c8e-4869-af80-0a4944a793a4@tu-dortmund.de

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/17ce344f86f1a9a9002d8b668ea7d77234ec3e60

Modified Files
--------------
src/backend/access/brin/brin_bloom.c | 19 +++++-------------
src/backend/access/brin/brin_inclusion.c | 31 +++++++++++++++++------------
src/backend/access/brin/brin_minmax_multi.c | 19 +++++-------------
3 files changed, 28 insertions(+), 41 deletions(-)