Move kernel baseline tests to front_end.

pkg/front_end/testcases/accessors.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.
 
 void set onlySetter(value) {
   print("onlySetter called with $value.");
 }
 
 class C {
   void set onlySetter(value) {
@@ skipping 28 matching lines @@
   try {
     print(onlySetter);
     throw "No error thrown";
   } on NoSuchMethodError catch (e) {
     print("Expected error: $e");
   }
   onlySetter = "fisk";
   new C().testC();
   new D().testD();
 }