Monitor MetalLB

1. Enable monitoring for MetalLB https://github.com/metallb/metallb/blob/main/charts/metallb/values.yaml#L17

to have access to metrics: https://metallb.universe.tf/prometheus-metrics/#metallb-bgp-metrics

2. Create alerting rules

3. Create Grafana dashboard

Addresses only BGP native mode. frr-k8s to be addressed in another issue