Split Strimzi Metrics Reporter defaults by Kafka node role

[MARKOCEVRLJAKOVIC]

Fixes #12181

Description

This change splits the default Strimzi Metrics Reporter allow list by Kafka node role.

• broker-only nodes use broker-specific metrics together with shared metrics
• controller-only nodes use controller-specific metrics together with shared metrics
• mixed broker/controller nodes continue using the combined default allow list
• custom values.allowList continues to take precedence for all node roles

The node-role selection is handled in KafkaCluster, while StrimziMetricsReporterModel remains role-agnostic by accepting the appropriate default allow list from the caller.

Testing

• Added unit tests for broker-only, controller-only and mixed-role default allow lists.
• Added tests verifying that custom allow lists override role-specific defaults.

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[scholzj]

Thanks for the PR. However, I think that is already being worked on in #12966

[MARKOCEVRLJAKOVIC]

Thanks for letting me know. There was no PR open for this issue when I started working on it. I'll close this one to avoid duplicate work. If useful, feel free to reuse any ideas or tests from this branch.

[scholzj]

Yeah, the PR is pretty new. Sorry. Maybe you can just write on the issue when you start working on it so that others know.