Use recommended kubegen script for code generation

[unmarshall]

How to categorize this issue?

/area open-source
/area dev-productivity
/kind enhancement

What would you like to be added:

• Start using kube_codegen.sh and regenerate deep copy functions.
• Generate typed client to directly interact with Etcd resources. We do not have any client right now and place this at the top level directory.
• Check if we can use https://github.com/kubernetes/code-generator/blob/master/examples/hack/verify-codegen.sh as part of CI/CD pipeline.

Why is this needed:

With k8s.io/*@v0.30.0 onwards the recommended way to generate code (defaulting functions, deep copy functions and client sets) is to use the new kube_codegen.sh (https://github.com/kubernetes/code-generator?tab=readme-ov-file). We have already moved to k8s.io/*@v0.31.0 but we have not adopted the recommendations w.r.t code generation.