Emit more metrics for broader visibility

[iamKunalGupta]

1. flow_status metrics: for every mirror emit a value of 1 with flowName and status metric labels, include unknown status as well
2. maintenance_running emit 1 with maintenance_type = start/end
3. flow_source_table_count emit table count for a given flowName
4. Add peerSourceType, peerSourceHost, and peerDestinationType,peerDestinationHost to all metrics emitted.
5. Whenever we add alert to catalog, emit the alert count as a metric
6. Add rows synced metric