feat(postgres): rename metrics from cnpg_pg_ to pg_

ref: #18

Author: jon-nfc

manifests/postgres/components/metrics/kustomization.yaml

@@ -22,6 +22,15 @@ patches:
           - sourceLabels: ["__meta_kubernetes_pod_name"]
             targetLabel: instance
             action: replace
+      
+      - op: add
+        path: /spec/monitoring/podMonitorMetricRelabelings
+        value:
+          - sourceLabels: [__name__]
+            regex: cnpg_pg_(.+)
+            targetLabel: __name__
+            replacement: pg_${1}
+            action: replace
     # yamllint enable rule:indentation
     target:
       group: postgresql.cnpg.io