[KYUUBI apache#6845] Support additional labels for PodMonitor to be d…

…iscovered by Prometheus

### Why are the changes needed?
the prometheus can not discover the podMonitor created by kyuubi helm chart.

### How was this patch tested?
1. enable pod monitor:
```
metrics:
  # Enable metrics system, used for 'kyuubi.metrics.enabled' property
  enabled: true
  # A comma-separated list of metrics reporters, used for 'kyuubi.metrics.reporters' property
  reporters: PROMETHEUS
  # Prometheus port, used for 'kyuubi.metrics.prometheus.port' property
  prometheusPort: 10019

  # PodMonitor by Prometheus Operator
  podMonitor:
    # Enable PodMonitor creation
    enabled: true
    # List of pod endpoints serving metrics to be scraped by Prometheus, see Prometheus Operator docs for more details
    #podMetricsEndpoints: []
    podMetricsEndpoints:
      - path: /metrics
        port: prometheus
```
2. Helm install kyuubi .
3. check prometheus web ui.

### Was this patch authored or co-authored using generative AI tooling?
No

Closes apache#6845 from eric9204/add-lab-to-pm.

Closes apache#6845

4d713a0 [Cheng Pan] Update charts/kyuubi/values.yaml
f8fa51f [dongsj] resolve conflicts with master

Lead-authored-by: dongsj <[email protected]>
Co-authored-by: Cheng Pan <[email protected]>
Signed-off-by: Cheng Pan <[email protected]>

charts/kyuubi/templates/kyuubi-podmonitor.yaml

@@ -22,6 +22,9 @@ metadata:
   name: {{ .Release.Name }}
   labels:
     {{- include "kyuubi.labels" . | nindent 4 }}
+    {{- if .Values.metrics.podMonitor.labels }}
+    {{- toYaml .Values.metrics.podMonitor.labels | nindent 4 }}
+    {{- end }}
 spec:
   selector:
     matchLabels:

charts/kyuubi/values.yaml

@@ -285,6 +285,8 @@ metrics:
     #  podMetricsEndpoints：
     #    - path: /metrics
     #      port: prometheus
+    # Additional labels for PodMonitor to be discovered by Prometheus
+    labels: {}
 
   # ServiceMonitor by Prometheus Operator
   serviceMonitor: