Improve config package names and reduce API exposure.

api/konfig/builtinpluginconsts/images.go

@@ -0,0 +1,10 @@
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package builtinpluginconsts
+
+const (
+	// imageFieldSpecs is left empty since `containers` and `initContainers`
+	// of *ANY* kind in *ANY* path are builtin supported in code
+	imagesFieldSpecs = ``
+)