Replace PG_STAT_STATEMENTS_LIMIT on exporter startup

The new variable was added for the `pg_stat_statements` support. This sets the default to be "20" statements, which is what is used by pgMonitor. Co-authored-by: Steven Siahetiong <ssiahetiong@exist.com> Issue: CrunchyData#2244

Author: ssiahetiong

bin/crunchy-postgres-exporter/start.sh

@@ -214,7 +214,7 @@ else
  fi
 fi
 
-sed -i "s/#PGBACKREST_INFO_THROTTLE_MINUTES#/${PGBACKREST_INFO_THROTTLE_MINUTES:-10}/g" /tmp/queries.yml
+sed -i -e "s/#PGBACKREST_INFO_THROTTLE_MINUTES#/${PGBACKREST_INFO_THROTTLE_MINUTES:-10}/g" -e "s/#PG_STAT_STATEMENTS_LIMIT#/${PG_STAT_STATEMENTS_LIMIT:-20}/g" /tmp/queries.yml
 
 PG_OPTIONS="--extend.query-path=${QUERY_DIR?}/queries.yml --web.listen-address=:${POSTGRES_EXPORTER_PORT}"