Add grafana example for haproxy monitoring

[mflendrich]

Issue originally authored by tnozicka as #1236

Is this a bug report or feature request?

• Feature Request

What should the feature do:
We should add grafana dashboard example to monitor haproxy instance in
https://github.com/scylladb/scylla-operator/tree/7b1f7235e30c02cc97e9c892278350c21a298493/examples/third-party/haproxy-ingress
There is already a prometheus example that it can use.

What is use case behind this feature:
observability

Additional Information: