[MKS] Public Cloud Load Balancer to support Prometheus endpoint creation using annotations

[antonin-a]

As a MKS user that automatically create LB using Kubernetes service type loadbalancer I would like to be able to export LB metrics to Prometheus so I can monitor my LB.

This is currently possible on Octavia side using a listener with "PROMETHEUS" protocol (https://docs.openstack.org/octavia/latest/user/guides/monitoring.html) but it does not exist on Openstack CCM.
The idea is to be able to configure it directly using annotations at Loadbalancer service creation.

An issue on Openstack CCM upstream project has been created to agree how to implement it: kubernetes/cloud-provider-openstack#2465

[MrOffline77]

We want to see and use this too ! Its incredible difficult to tell when to scale up now with the LBs.

[nicolaslacroux]

We have opened a pull request on upstream repository:
kubernetes/cloud-provider-openstack#2633