Move package_manager into mojo/shell

mojo/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",
-    "package_manager_impl.cc",
-    "package_manager_impl.h",
-  ]
-
-  deps = [
-    "//mojo/fetcher",
-    "//mojo/shell",
-    "//mojo/util:filename_util",
-  ]
-}
-
-test("unittests") {
-  output_name = "mojo_package_manager_unittests"
-
-  sources = [
-    "capability_filter_content_handler_unittest.cc",
-    "content_handler_unittest.cc",
-  ]
-
-  deps = [
-    ":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",
-  ]
-}