Add prometheus and grafana to the Monocle compose file

[morucci]

A Prometheus basic probe has been integrated into Monocle. A demo of a Grafana dashboard has been provided in https://github.com/change-metrics/monocle/pull/539. This issue is to implement the follow-up.

• [ ] Add an option to the Monocle compose to deploy the monitoring components
• [ ] Handle basic configuration setting as env vars (creds, ...)