Ensure OpenAPI schema is accurate in the Gateway types

[dprotaso]

Without the correct annotations Server Side Apply won't work properly.

For example in upstream K8s the PodSpec OpenAPI schema didn't have the correct x-kubernetes-list-map-keys & x-kubernetes-list-type so you couldn't separate ownership of different containers.

The purpose of the issue is to audit the schema of our types and ensure accuracy

Originally posted by @dprotaso in #2537 (comment)