Let DMS export rule files of DNPs

[Marketen]

Some panels of grafana dashboards need to configure Prometheus rules in order to work properly. For example, geth's official prometheus dashboard: https://grafana.com/grafana/dashboards/18463-go-ethereum-by-instance/

Adding this to DMS would require to:

• search for a specific file name in every DNP. For example *-prom-rules.yml.
  • If file exists, modify prometheus.yml & add *-prom-rules.yml file of the DNP to prometheus server filesystem.
  • If file doesnt exist, do nothing

More info on prometheus rules: https://prometheus.io/docs/prometheus/latest/configuration/recording_rules/