Merge pull request #53651 from sttts/sttts-apis-core

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>.

Move core API to pkg/apis/core

Fixes https://github.com/kubernetes/kubernetes/issues/55304.

This moves the types in pkg/api and most of pkg/api/v1 to pkg/apis/core to match the other api groups, following-up on what https://github.com/kubernetes/kubernetes/pull/44784 did for the external types.

It's a nearly 100% mechanical package move with a number of trivial fixups in code-generators and in tests which do string comparisons of types via reflection.

**Most importantly:**

- group names are unchanged
- apimachinery semantics are unchanged
- the outside api is unchanged.

Note that some packages for helpers are left in pkg/api/v1. Splitting them into helpers which belong tightly to the api and those which are not is left to follow-ups.

@kubernetes/sig-api-machinery-pr-reviews

Kubernetes-commit: dd9981d038012c120525c9e6df98b3beb3ef19e1

pkg/admission/plugin/webhook/authentication.go

@@ -17,12 +17,11 @@ limitations under the License.
 package webhook
 
 import (
+	"fmt"
 	"io/ioutil"
 	"strings"
 	"time"
 
-	"fmt"
-
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
 	clientcmdapi "k8s.io/client-go/tools/clientcmd/api"