Add an operator label to the KubernetesPodOperator task
It was observed that the test task that uses the KubernetesPodOperator was unable to access the Kubernetes API, owing to a missing networkpolicy.
Rather than allow all task pods to contact the API, we have submitted https://gerrit.wikimedia.org/r/c/operations/deployment-charts/+/1110883 ...to grant these permissions only to airflow task pods with a label of 'operator' which is set to one of a named list of values that correspod to those listed at: https://airflow.apache.org/docs/apache-airflow-providers-cncf-kubernetes/stable/operators.html
Bug: T383430