Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/cache/add/all_adds_all_matching_versions_test.dart

-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library pub_tests;
-
-import '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration('"--all" adds all matching versions of the package', () {
-    servePackages((builder) {
-      builder.serve("foo", "1.2.2");
-      builder.serve("foo", "1.2.3-dev");
-      builder.serve("foo", "1.2.3");
-      builder.serve("foo", "2.0.0");
-    });
-
-    schedulePub(
-        args: ["cache", "add", "foo", "-v", ">=1.0.0 <2.0.0", "--all"],
-        output: '''
-          Downloading foo 1.2.2...
-          Downloading foo 1.2.3-dev...
-          Downloading foo 1.2.3...''');
-
-    d.cacheDir({
-      "foo": "1.2.2"
-    }).validate();
-    d.cacheDir({
-      "foo": "1.2.3-dev"
-    }).validate();
-    d.cacheDir({
-      "foo": "1.2.3"
-    }).validate();
-  });
-}