Set shared_preload_libraries = pg_stat_statements on all pg servers

This is used for metrics by the prometheus sql exporter.

Test Plan

*** Running octocatalog-diff on host db1.internal.staging.swh.network
I, [2021-09-09T19:12:24.537228 #3374991]  INFO -- : Catalogs compiled for db1.internal.staging.swh.network
I, [2021-09-09T19:12:24.875789 #3374991]  INFO -- : Diffs computed for db1.internal.staging.swh.network
diff origin/production/db1.internal.staging.swh.network current/db1.internal.staging.swh.network
*******************************************
+ Postgresql::Server::Config_entry[shared_preload_libraries] =>
   parameters =>
      "ensure": "present"
      "path": false
      "value": "pg_stat_statements"
*******************************************
+ Postgresql_conf[shared_preload_libraries] =>
   parameters =>
      "ensure": "present"
      "notify": "Class[Postgresql::Server::Service]"
      "target": "/etc/postgresql/12/main/postgresql.conf"
      "value": "pg_stat_statements"
*******************************************
*** End octocatalog-diff on db1.internal.staging.swh.network
*** Running octocatalog-diff on host bardo.internal.admin.swh.network
I, [2021-09-09T19:12:29.036842 #3375144]  INFO -- : Catalogs compiled for bardo.internal.admin.swh.network
I, [2021-09-09T19:12:29.334533 #3375144]  INFO -- : Diffs computed for bardo.internal.admin.swh.network
diff origin/production/bardo.internal.admin.swh.network current/bardo.internal.admin.swh.network
*******************************************
+ Postgresql::Server::Config_entry[shared_preload_libraries] =>
   parameters =>
      "ensure": "present"
      "path": false
      "value": "pg_stat_statements"
*******************************************
+ Postgresql_conf[shared_preload_libraries] =>
   parameters =>
      "ensure": "present"
      "notify": "Class[Postgresql::Server::Service]"
      "target": "/etc/postgresql/12/main/postgresql.conf"
      "value": "pg_stat_statements"
*******************************************
*** End octocatalog-diff on bardo.internal.admin.swh.network

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Migrated from D6236 (view on Phabricator)