pgsql: pg_stat_statements: Add counters for generic and custom plans

pg_stat_statements: Add counters for generic and custom plans

This patch adds two new counters to pg_stat_statements:
- generic_plan_calls
- custom_plan_calls

These counters track how many times a prepared statement was executed
using a generic or custom plan, respectively, providing a global
equivalent at query level, for top and non-top levels, of
pg_prepared_statements whose data is restricted to a single session.

This commit builds upon e125e360020a.  The module is bumped to version
1.13.  PGSS_FILE_HEADER is bumped as well, something that the latest
patches touching the on-disk format of the PGSS file did not actually
bother with since 2022..

Author: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Ilia Evdokimov <ilya.evdokimov@tantorlabs.com>
Reviewed-by: Andrei Lepikhov <lepihov@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Nikolay Samokhvalov <nik@postgres.ai>
Discussion: https://postgr.es/m/CAA5RZ0uFw8Y9GCFvafhC=OA8NnMqVZyzXPfv_EePOt+iv1T-qQ@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/3357471cf9f5e470dfed0c7919bcf31c7efaf2b9

Modified Files
--------------
contrib/pg_stat_statements/Makefile                |   3 +-
.../pg_stat_statements/expected/oldextversions.out |  67 ++++++
contrib/pg_stat_statements/expected/plancache.out  | 224 +++++++++++++++++++++
contrib/pg_stat_statements/meson.build             |   2 +
.../pg_stat_statements--1.12--1.13.sql             |  78 +++++++
contrib/pg_stat_statements/pg_stat_statements.c    |  53 ++++-
.../pg_stat_statements/pg_stat_statements.control  |   2 +-
contrib/pg_stat_statements/sql/oldextversions.sql  |   5 +
contrib/pg_stat_statements/sql/plancache.sql       |  94 +++++++++
doc/src/sgml/pgstatstatements.sgml                 |  18 ++
10 files changed, 536 insertions(+), 10 deletions(-)