chore: ensure metrics are correctly exposed

[maltesander]

Description

Part of stackabletech/issues#747
This PR adds a metrics service with the additional Prometheus annotations.
The metrics service is also added to the TLS cert in order to scrape the metrics service.

BREAKING:

• Renamed the <stacklet>-<role>-<rolegroup> service to <stacklet>-<role>-<rolegroup>-headless.
• Switched metrics port exposure and annotations to native prom metrics instead of JMX.

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

Author

• Changes are OpenShift compatible
• CRD changes approved
• CRD documentation for all fields, following the style guide.
• Helm chart can be installed and deployed operator works
• Integration tests passed (for non trivial changes)
• Changes need to be "offline" compatible
• Links to generated (nightly) docs added
• Release note snippet added

Reviewer

• Code contains useful comments
• Code contains useful logging statements
• (Integration-)Test cases added
• Documentation added or updated. Follows the style guide.
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added
• Links to generated (nightly) docs added
• Release note snippet added
• Add type/deprecation label & add to the deprecation schedule
• Add type/experimental label & add to the experimental features tracker

[adwk67]

LGTM!

[adwk67]

Do we need a changelog entry, as this is sort-of user-facing?

[adwk67]

Thanks!

[maltesander]

Release snippet

This is a combined summary of this PR and the headless revert #726.

The metrics format changed, so this is possibly breaking (native vs jmx)

Previously, the hdfs-operator did not expose Prometheus annotations containing the http(s) scheme or the metrics path and port. This was added in this PR and allows custom relabel configs in Prometheus to use these annotations to scrape the metric endpoints.
The metrics service now serves native Prometheus metrics instead of JMX metrics, which are reachable under the `jmx-metrics` port (Note: this changes the metrics output).