Migrate to new K8s generator scripts/go commands

## Context
See https://cloud-native.slack.com/archives/C04LGHDR9K7/p1704710449414709 and https://github.com/knative/pkg/pull/2904

## Possible solutions
Based on https://github.com/knative/pkg/pull/2904#issuecomment-1851613905 and discussions.

a) Use `go run` instead of scripts (downside: this does not clean up old resources)
b) Use the new `k8s.io/code-generator/kube_codegen.sh`
c) Wait until @cardil manages to migrate the scripts in K8s to full golang, then adapt to that solution

## Todo
- [ ] Agree on which way to go
- [ ] Implement in `pkg`
- [ ] Implement on all downstream repos

Start by reviewing the linked knative/pkg pull request and the Kubernetes generator options described here, especially go run and kube_codegen.sh. The issue first needs agreement on an approach, then implementation in pkg and migration of all downstream repositories; done means those decisions and migrations are complete.

Written by the indexing model from the issue text.