[kube-prometheus-stack] let additionalRuleGroupLabels override additionalRuleLabels

[michaelruigrok]

What this PR does / why we need it

This PR ensures that rule annotations and labels that are specific to a rule group -- i.e., the ones set in .Values.defaultRules.additionalRuleGroup(Labels|Annotations) -- will override values set in the global defaults (e.g. .defaultRules.additionalRuleLabels). Specifically, this change allows the following configuration, which applies a global label except to rules which would break if such labels were applied.

defaultRules:
  additionalRules:
    cluster: cluster-nam

  additionalRuleGroupLabels:
    kubeApiserverAvailability:
      cluster: null

This provides a workaround to #3396, where a rule in kube-apiserver-availability.rules will fail when labels are applied to it.

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• mitigates [kube-prometheus-stack] additionalRuleLabels shouldn't apply to recording rules #3396

Special notes for your reviewer

I am unsure if releases are performed for every PR, or PRs are held for larger releases. As such I have not bumped the chart version for this PR. Please let me know if I should do so, thanks.

Checklist

• DCO signed
• Chart Version bumped
• Title of the PR starts with chart name (e.g. [prometheus-couchdb-exporter])

[jkroepke]

Thats not a great condition. It prevent label values like 0 or false.

[michaelruigrok]

You're right, thank you I'll fix this up