Automatic merge from submit-queue (batch tested with PRs 64613, 64596, 64573, 64154, 64639). 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>.

Openapi some cleanup

Clean-up some OpenAPI code, mostly test related (there are two implementations of "Fake").
This is going for master, but I'll probably also cherry-pick/create a similar PR for feature-serverside-apply branch since we'll need that to move some code around.

**What this PR does / why we need it**:

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```