Move kernel baseline tests to front_end.

pkg/front_end/test/fasta/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;
-}