Automatic merge from submit-queue (batch tested with PRs 40289, 40877, 40879, 39972, 40942)

Extract util used by jsonmergepatch and SMPatch

followup  https://github.com/kubernetes/kubernetes/pull/40666#discussion_r99198931

Extract some util out of the `strategicMergePatch` to make `jsonMergePatch` doesn't depend on `strategicMergePatch`.

```release-note
None
```

cc: @liggitt