Move mojo edk into mojo/edk

mojo/tools/BUILD.gn

 # Copyright 2014 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.
 
 # GYP version: mojo/mojo_base.gyp:mojo_message_generator
 executable("message_generator") {
   testonly = true
   output_name = "mojo_message_generator"
 
   sources = [
     "message_generator.cc",
   ]
 
   deps = [
     "//base",
     "//mojo/common",
+    "//mojo/edk/system",
+    "//mojo/environment:chromium",
     "//mojo/public/cpp/bindings",
-    "//mojo/environment:chromium",
-    "//mojo/system",
     "//testing/gtest",
   ]
 }