Move all tests using dart:io to a separate directory

tests/standalone/src/io/ChunkedStreamTest.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.
 
 #import("dart:io");
 #import("dart:isolate");
 
 void test1() {
   void testWithChunkSize(var data, int chunkSize, Function testDone) {
     InputStream list_input_stream = new ListInputStream();
@@ skipping 120 matching lines @@
   s.write([4, 5, 6]);  // 7 bytes written to stream.
 
   donePort.receive((x,y) => donePort.close());
 }
 
 
 main() {
   test1();
   test2();
 }