Move kernel baseline tests to front_end.

pkg/front_end/testcases/rasta/super_initializer.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.md file.
 
 class Super {
   Super.arg0();
   Super.arg1(a);
   Super.arg2(a, b);
 }
 
 class Sub extends Super {
   var field;
   Sub.arg0() : super.arg0(), field = 42;
   Sub.arg1(a) : super.arg1(a), field = 42;
   Sub.arg2(a, b) : super.arg2(a, b), field = 42;
 }