Automatic merge from submit-queue (batch tested with PRs 44406, 41543, 44071, 44374, 44299)

Move pkg/api/ref.go to a subpackage

First commit is #44296. (unfortunately, removing that commit results in conflicts)

This PR moves the pkg/api/ref.go to its own subpackage. It's mostly a mechanic move.

I'll send a few more PRs to make the k8s.io/kubernetes/pkg/api package only contains the code we want in the k8s.io/api repo, then we can run a [script](https://github.com/kubernetes/kubernetes/pull/41747/commits/a0015fd1be6c6a239fc40cc3c04ba5ed7b1ab22e#diff-7a2fbb4371972350ee414c6b88aee1c8) to cut the new repo.