Harry Cho

Add pg_stat_wal table metrics

1

* Adds the following metrics. [pg_stat_wal table](https://www.postgresql.org/docs/16/monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW). It is off by default ``` "wal_records", "wal_fpi", // bigint "wal_bytes", // numeric "wal_buffers_full", // bigint "wal_write", // bigint "wal_sync", // bigint "wal_write_time",...