Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
staging: add boilerplate header
Follow up of https://github.com/kubernetes/kubernetes/pull/57656.
Adds boilerplate in the relevant staging repos so that they don't need to depend on code-generator's boilerplate.
**Release note**:
```release-note
NONE
```
/cc sttts fisherxu
Kubernetes-commit: 1a1643bb5df07d94330e1b16d182cee660533f91
a101c83a5e