Prometheus monitoring router max connections numbers

1. Proposed title of this feature request
Please add a function in OCP Prometheus to monitoring router max connections

2. Why does the customer need this? (List the business requirements here)

Because of the OCP haproxy router pod, can not changed the max connection numbers, so please add a warning ruls and monitoring rules to help the customer monitor the max connection on haproxy router, when the max connection will full the customer can add more router pod