text: Title: [k8s] Make `ports: ingress` reuse API server's nginx controller
  Body: Currently if users deploy the API server with our helm chart, we create an ingress controller and expose it through a NodePort svc (or optionally, LoadBalancer svc).
  
  We can (and should) piggyback on this existing ingress controller for exposing ports via [`ports: ingress` mode](https://docs.skypilot.co/en/latest/reference/kubernetes/kubernetes-ports.html#nginx-ingress). This would eliminate the need for users to set up another nginx ingress controller and re-use the same public facing NodePort/LoadBalancer service.