Rationalize Dart mojo and sky package structure

examples/dart/netcat/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//mojo/public/dart/rules.gni")
 
-dart_packaged_application("netcat") {
+dartzip_packaged_application("netcat") {
   sources = [
     "main.dart",
   ]
   deps = [
     "//mojo/public/dart",
     "//mojo/services/files/public/interfaces",
     "//mojo/services/network/public/interfaces",
     "//mojo/services/terminal/public/interfaces",
   ]
 }