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>.

apiextensions: add round trip tests for CRD schema conversion

Follow up test for https://github.com/kubernetes/kubernetes/pull/52281.

Need to update go-openapi to get this - https://github.com/go-openapi/spec/pull/31 - in.

**Special notes for your reviewer**: The tests won't pass until https://github.com/kubernetes/kubernetes/pull/52281 is merged.

**Release note**:

```release-note
NONE
```

/cc @sttts