Add "pub global list" command to show all globally activated packages.

sdk/lib/_internal/pub/test/global/deactivate/path_package_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.
 
 import 'package:path/path.dart' as p;
 
 import '../../../lib/src/io.dart';
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   integration('deactivates an active path package', () {
     d.dir("foo", [
       d.libPubspec("foo", "1.0.0"),
       d.dir("bin", [
         d.file("foo.dart", "main() => print('ok');")
       ])
     ]).create();
 
     schedulePub(args: ["global", "activate", "--source", "path", "../foo"]);
 
     var path = canonicalize(p.join(sandboxDir, "foo"));
     schedulePub(args: ["global", "deactivate", "foo"],
-        output: 'Deactivated package foo at path "$path".');
+        output: 'Deactivated package foo 1.0.0 at path "$path".');
   });
 }