pgsql: Use palloc_object() and palloc_array(), the last change

Use palloc_object() and palloc_array(), the last change

This is the last batch of changes that have been suggested by the
author, this part covering the non-trivial changes. Some of the changes
suggested have been discarded as they seem to lead to more instructions
generated, leaving the parts that can be qualified as in-place
replacements.

Similar work has been done in 1b105f9472bd, 0c3c5c3b06a3 and
31d3847a37be.

Author: David Geier <geidav(dot)pg(at)gmail(dot)com>
Discussion: https://postgr.es/m/ad0748d4-3080-436e-b0bc-ac8f86a3466a@gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/4f7dacc5b82af19788599671abe4ac633fd7ea4c

Modified Files
--------------
contrib/pg_buffercache/pg_buffercache_pages.c | 8 ++++----
contrib/pg_trgm/trgm_op.c | 14 +++++++-------
contrib/postgres_fdw/postgres_fdw.c | 20 +++++++++----------
src/backend/executor/execPartition.c | 28 +++++++++++----------------
src/backend/partitioning/partprune.c | 23 +++++++++++-----------
src/backend/statistics/mvdistinct.c | 14 +++++++-------
src/backend/storage/buffer/bufmgr.c | 6 +++---
7 files changed, 53 insertions(+), 60 deletions(-)