Support Custom Service Port Names

[eahrend]

We have a use case where we want to attach our kong gateway to our istio based service mesh, however in order for the metrics to be presented, we need to name our service ports and currently that is not doable in the current kong setup.

https://cloud.google.com/service-mesh/docs/onboarding/kubernetes-workloads?hl=en#name_service_ports

What I am proposing:

• Add two values to the values files
  • http-service-port-prefix
    • this will prefix all http service ports with the prefix listed, if it exists
  • https-service-port-prefix
    • this will prefix all https service ports with the prefix listed, if it exists