Introduce GroupVersioner for capturing desired target version

Convert single GV and lists of GVs into an interface that can handle
more complex scenarios (everything internal, nothing supported). Pass
the interface down into conversion.

pkg/client/unversioned/clientcmd/api/latest/latest.go

@@ -60,7 +60,7 @@ func init() {
 		Scheme,
 		yamlSerializer,
 		yamlSerializer,
-		[]unversioned.GroupVersion{{Version: Version}},
-		[]unversioned.GroupVersion{{Version: runtime.APIVersionInternal}},
+		unversioned.GroupVersion{Version: Version},
+		runtime.InternalGroupVersioner,
 	)
 }