Move pub into sdk/lib/_internal.

sdk/lib/_internal/pub/test/install/git/check_out_with_trailing_slash_test.dart

 // Copyright (c) 2012, 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 'dart:io';
 
 import 'package:scheduled_test/scheduled_test.dart';
 
@@ skipping 24 matching lines @@
       ]).validate();
 
       d.dir(packagesPath, [
         d.dir('foo', [
           d.file('foo.dart', 'main() => "foo";')
         ])
       ]).validate();
     });
   });
 }