Move kernel baseline tests to front_end.

pkg/kernel/testcases/input/store_load.dart

-// Copyright (c) 2016, 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.
-class Foo {
-  var _field;
-}
-
-class FooValue {}
-
-class Bar {
-  var _field; // Same name.
-}
-
-class BarValue {}
-
-main() {
-  var foo = new Foo();
-  foo._field = new FooValue();
-  var fooValue = foo._field;
-  print(fooValue);
-
-  var bar = new Bar();
-  bar._field = new BarValue();
-  var barValue = bar._field;
-  print(barValue);
-}