Resolve "Istio operator template - allow for changing labels for extra gateways"

Closes #13 (closed)

We kinda backed ourselves into a corner with the values.yaml spec, so I decided to keep it the same rather than modify the existing spec.

That means it looks kinda weird that .Values.ingressGateway.podAnnotations is how you set for the primary ingressgateway, but .Values.extraIngressGateways.*.k8s.podAnnotations is how you set it for the extra gateways.