Move package_manager into mojo/shell

mojo/shell/package_manager/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("//testing/test.gni")
 
 source_set("package_manager") {
   sources = [
     "content_handler_connection.cc",
     "content_handler_connection.h",
@@ skipping 20 matching lines @@
     ":package_manager",
     "//base",
     "//mojo/application/public/cpp",
     "//mojo/shell",
     "//mojo/shell:test_support",
     "//testing/gtest",
     "//third_party/mojo/src/mojo/edk/test:run_all_unittests",
     "//url",
   ]
 }