Support custom labels on Pods created by clickhouseinstallations

[klibr007]

Description

When deploying a ClickHouseInstallation, there does not appear to be a supported way to add custom labels to the Pods created by the operator.

We would like to apply custom organizational labels to all ClickhousePods generated by a ClickHouseInstallation, without relying on external mutating admission controllers or post-deployment patches.

For example:

metadata:
  labels:
    xxx: yyy

or

spec:
  templates:
    podTemplates:
      podLabels:
        xxx: yyy

which would then be propagated to the Pod templates of the generated StatefulSets.