pgsql: Simplify SRFs using materialize mode in contrib/ modules

Simplify SRFs using materialize mode in contrib/ modules

9e98583 introduced a helper to centralize building their needed state
(tuplestore, tuple descriptors, etc.), checking for any errors. This
commit updates all places of contrib/ that can be switched to use
SetSingleFuncCall() as a drop-in replacement, resulting in the removal
of a lot of boilerplate code in all the modules updated by this commit.

Per analysis, some places remain as they are:
- pg_logdir_ls() in adminpack/ uses historically TYPEFUNC_RECORD as
return type, and I suspect that changing it may cause issues at run-time
with some of its past versions, down to 1.0.
- dblink/ uses a wrapper function doing exactly the work of
SetSingleFuncCall(). Here the switch should be possible, but rather
invasive so it does not seem the extra backpatch maintenance cost.
- tablefunc/, similarly, uses multiple helper functions with portions of
SetSingleFuncCall() spread across the code paths of this module.

Author: Melanie Plageman
Discussion: https://postgr.es/m/CAAKRu_bvDPJoL9mH6eYwvBpPtTGQwbDzfJbCM-OjkSZDu5yTPg@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/5b81703787bfc1e6072c8e37125eba0c5598b807

Modified Files
--------------
contrib/amcheck/verify_heapam.c | 46 ++--------------
contrib/dblink/dblink.c | 26 +--------
contrib/pageinspect/brinfuncs.c | 31 ++---------
contrib/pageinspect/gistfuncs.c | 60 ++-------------------
contrib/pg_stat_statements/pg_stat_statements.c | 33 ++----------
contrib/pgrowlocks/pgrowlocks.c | 34 ++----------
contrib/postgres_fdw/connection.c | 31 +----------
contrib/xml2/xpath.c | 72 ++++---------------------
8 files changed, 32 insertions(+), 301 deletions(-)