Make included Prometheus server configurable

[MBcom]

The prometheus configuration is currently hardcoded. Extending it is not possible - e.g. connecting it with an external alert manager. We want to connect the included Prometheus server to an external Alert Manager which is currently not possible.

Describe the solution you'd like Allow to modify the prometheus configuration entirely in values.yaml

Describe alternatives you've considered We think that making only external Alert Managers configurable would not catch all possible wishes against prometheus configuration.

Additional context