pgsql: pg_stat_statements: Add regression test for privilege handling.

pg_stat_statements: Add regression test for privilege handling.

This commit adds a regression test to verify that pg_stat_statements
correctly handles privileges, improving its test coverage.

Author: Keisuke Kuroda
Reviewed-by: Michael Paquier, Fujii Masao
Discussion: https://postgr.es/m/2224ccf2e12c41ccb81702ef3303d5ac@nttcom.co.jp

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/97f2bc5aa531e32e91c7f27aeaeb87a07e13e822

Modified Files
--------------
contrib/pg_stat_statements/Makefile                |  3 +-
contrib/pg_stat_statements/expected/privileges.out | 97 ++++++++++++++++++++++
contrib/pg_stat_statements/meson.build             |  1 +
contrib/pg_stat_statements/sql/privileges.sql      | 60 +++++++++++++
4 files changed, 160 insertions(+), 1 deletion(-)