Migrate from nginx-ingress-controller to istio

[ensonic]

Since the nginx-ingress controller is deprecated prepare the transition to istio using the gateways api through the followign steps:

• add a config.sh variable USE_ISTIO (default false) and pass as a helm variable
• add the istio resources to the codebase and use helm variable to install either nginx-ingress-controller or istio
• run ingress2gateway tool to port the ingress resources in the codebase, depending on the helm variable install either the old ingress resources or the http/grpc routes + gateway resources