Move isolate tests to lib/isolate.

tests/isolate/typed_message_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.
 // Dart test program for testing isolate communication with
 // typed objects.
 // VMOptions=--checked
 
 library TypedMessageTest;
 import "dart:async";
 import "package:expect/expect.dart";
@@ skipping 30 matching lines @@
   iterator.moveNext().then((b) {
     SendPort sendPort = iterator.current;
     sendPort.send(msg);
     return iterator.moveNext();
   }).then((b) {
     Expect.equals(1, iterator.current);
     receivePort.close();
     asyncEnd();
   });
 }