Refinery - add option to generate ServiceMonitor

[Mike Robinson]

Is your feature request related to a problem? Please describe.

This request is similar to #14, but for Refinery.

Currently when Refinery is released with PrometheusMetrics.enabled: true (default), the deployment is automatically annotated such that a running Prometheus instance will scrape the relevant endpoint. Generally this is fine, but does not support more advanced configuration options, such as relabeling or dropping certain metrics.

Describe the solution you'd like

One of two possible outcomes:

1. Provide the option to create a ServiceMonitor similar to the feature request made in #14.
2. Provide the option to provide an existing ServiceMonitor, and by doing so skipping the prometheus annotations in the deployment.

Describe alternatives you've considered

None; currently using the existing pod annotations.

Additional context

Dropping certain metrics can become necessary if an org is attempting to trim some observability costs with a vendor, like the reason Refinery exists 😃