Automatic merge from submit-queue (batch tested with PRs 44440, 44038, 44302, 44316, 43876)

Move pkg/api/ref.go and pkg/api/resource_helpers.go to subpackages

First two commits are #44296 #44299. (unfortunately, removing these commits results in conflicts)

This PR moves resource_helpers.go to a subpackage. It's mostly a mechanic move, except that:
* i kept the methods of ResourceName and ResourceList in pkg/api/method.go

I'll send one more PR to separate api.Scheme etc. to their own package.