Update code generation scripts with k8s v1.30 libraries

[mtardy]

Commit a9c509f replaced execution of deprecated scripts with k8s.io/code-generator/kube_codegen.sh. However, kube_codegen.sh doesn't generate code on its own, but rather defines helper functions. To migrate to kube_codegen.sh we'll need to call these functions from another script. Additionally, it'll change with version 1.30 of k8s libraries - that's why I opted to simply revert the change for now. When k8s libraries are updated to 1.30, the code generation scripts should be updated too.

_Originally posted by @lambdanis in #2339