Switch API objects to not register per version codecs

Remove Codec from versionInterfaces in meta (RESTMapper is now agnostic
to codec and serialization). Register api/latest.Codecs as the codec
factory and use latest.Codecs.LegacyCodec(version) as an equvialent to
the previous codec.

pkg/api/v1/defaults_test.go

@@ -28,12 +28,13 @@ import (
 )
 
 func roundTrip(t *testing.T, obj runtime.Object) runtime.Object {
-	data, err := versioned.Codec.Encode(obj)
+	codec := api.Codecs.LegacyCodec(versioned.SchemeGroupVersion)
+	data, err := runtime.Encode(codec, obj)
 	if err != nil {
 		t.Errorf("%v\n %#v", err, obj)
 		return nil
 	}
-	obj2, err := api.Codec.Decode(data)
+	obj2, err := runtime.Decode(codec, data)
 	if err != nil {
 		t.Errorf("%v\nData: %s\nSource: %#v", err, string(data), obj)
 		return nil