Migrate cluster ingress to GKE Gateway API

[danisla]

Instead of creating the GCLB, Managed Certs and AutoNEG controller for the ingress tier, create the GCLB using the new Gateway API.

This will reduce the manual dependencies and deployment complexity.

[kili-ilo]

Note to self: https://cloud.google.com/kubernetes-engine/docs/concepts/gateway-api