[K8S][HELM] Support additional labels for PrometheusRule

[dnskr]

Why are the changes needed?

The change is needed to be able to add additional labels to PrometheusRule similar to podMonitor and serviceMonitor.
The PR also includes minor identation fixes.

How was this patch tested?

helm template kyuubi charts/kyuubi --set metrics.prometheusRule.enabled=true --set metrics.prometheusRule.labels.test-label=true -s templates/kyuubi-alert.yaml
---
# Source: kyuubi/templates/kyuubi-alert.yaml
apiVersion: monitoring.coreos.com/v1
kind: PrometheusRule
metadata:
  name: kyuubi
  labels:
    helm.sh/chart: kyuubi-0.1.0
    app.kubernetes.io/name: kyuubi
    app.kubernetes.io/instance: kyuubi
    app.kubernetes.io/version: "1.10.0"
    app.kubernetes.io/managed-by: Helm
    test-label: true
spec:
  groups:
    []

Was this patch authored or co-authored using generative AI tooling?

No

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 0.00%. Comparing base (5237227) to head (234d99d).

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #7105   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files         697     697           
  Lines       43214   43214           
  Branches     5855    5855           
======================================
  Misses      43214   43214           

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[pan3793]

Hmm... why keep 6 leading spaces but | nindent 4

[dnskr]

It is quite a common pattern to use indentation for blocks to improve the readability of templates and it is mentioned in Best Practices for templates.

For instance, if we add common labels to all metric resources, the template without indentation looks as follows:

metadata:
  name: {{ .Release.Name }}
  labels:
    {{- include "kyuubi.labels" . | nindent 4 }}
    {{- if .Values.metrics.labels }}
    {{- toYaml .Values.metrics.labels | nindent 4 }}
    {{- end }}
    {{- if .Values.metrics.podMonitor.labels }}
    {{- toYaml .Values.metrics.podMonitor.labels | nindent 4 }}
    {{- end }}

but with indentation, it would be clearer that we have three sources for labels:

metadata:
  name: {{ .Release.Name }}
  labels:
    {{- include "kyuubi.labels" . | nindent 4 }}
    {{- if .Values.metrics.labels }}
      {{- toYaml .Values.metrics.labels | nindent 4 }}
    {{- end }}
    {{- if .Values.metrics.podMonitor.labels }}
      {{- toYaml .Values.metrics.podMonitor.labels | nindent 4 }}
    {{- end }}

[pan3793]

Thanks, merged to master