Move all tests using dart:io to a separate directory

tests/standalone/src/ReadIntoConstList.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.
-
-// Regression test for missing immutability check in the ListSet
-// methods in the API. This allowed overwriting const Lists.
-
-String getFilename(String path) =>
-    new File(path).existsSync() ? path : 'runtime/' + path;
-
-void main() {
-  var a = const [0];
-  var b = const [0];
-  Expect.isTrue(a === b);
-
-  String filename = getFilename("bin/file_test.cc");
-  File file = new File(filename);
-  InputStream input = file.openInputStream();
-  try {
-    input.readInto(a, 0, 1);
-    Expect.fail("no exception thrown");
-  } catch (var e) {
-    Expect.isTrue(e is FileIOException);
-  }
-  Expect.equals(0, a[0]);
-  Expect.equals(0, b[0]);
-}