apache / cloudberry

Turns out, `CREATE EXTENSION pg_buffercache` does not work on main. It is failing due pg_buffercache_usage_counts function is missing. This function was committed to PostgreSQL as part of https://github.com/postgres/postgres/commit/f3fa31327ecba75ee0e946abaa56dbf471ba704b Extension sql 1.4.1 version was cherry-picked to Cloudberry as part of https://github.com/apache/cloudberry/pull/883/ (see commit 79f2d28ea05e0746170be07386fe728e1003aaac) ``` CREATE EXTENSION pg_buffercache; +ERROR: function pg_buffercache_usage_counts() does not exist ``` This pr fixes cherry-pick issues, and adds this extension to `ic-contrib` check Found during PG16 rebase work Original commit msg: It was pointed out that pg_buffercache_summary()'s report of the overall average usage count isn't that useful, and what would be more helpful in many cases is to report totals for each possible usage count. Add a new function to do it like that. Since pg_buffercache 1.4 is already new for v16, we don't need to create a new extension version; we'll just define this as part of 1.4. Nathan Bossart Discussion: https://postgr.es/m/20230130233040.GA2800702@nathanxps13