Setup monitoring/prometheus-operator-kube-proxy metrics

[vijay-veeranki]

With the promethus-operator upgrade to 8.7.0, we now have a option to get option to scrape kube-proxy. But as it is available in kube-system, we are not able to get the metrics and getting the below error

https://prometheus.cloud-platform.service.justice.gov.uk/targets#job-monitoring%2fprometheus-operator-kube-proxy%2f0

Investigate options to get it working.

helm/charts#16476
kubernetes/kops#6472 (comment)

From the values file.

## Component scraping kube proxy
##
kubeProxy:
  enabled: true

  ## If your kube proxy is not deployed as a pod, specify IPs it can be found on
  ##
  endpoints: []
  # - 10.141.4.22
  # - 10.141.4.23
  # - 10.141.4.24

  service:
    port: 10249
    targetPort: 10249
    # selector:
    #   k8s-app: kube-proxy

  serviceMonitor:
    ## Scrape interval. If not set, the Prometheus default scrape interval is used.
    ##
    interval: ""

[AntonyBishop]

Related to #1850