[Platform] Define new metrics for async replication lag on the table level

[atarw]

Define new metrics to monitor/alert async replication on the table level. Currently we support monitoring and alerting about async replication lag metrics on the universe level (relevant code below).

https://github.com/yugabyte/yugabyte-db/blob/master/managed/src/main/resources/metrics.yml#L1973

https://github.com/yugabyte/yugabyte-db/blob/master/managed/src/main/java/com/yugabyte/yw/common/AlertDefinitionTemplate.java#L10

[hsu880]

This may have a DB dependency.