Move kernel baseline tests to front_end.

pkg/front_end/test/fasta/rasta/super_operator.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 A {
-  operator + (String s) => null;
-
-  operator [] (i) => null;
-
-  operator []= (i, val) {}
-}
-
-class B extends A {
-  operator + (String s) => super + ("${s}${s}");
-
-  operator [] (i) => super[i];
-
-  operator []= (i, val) => super[i++] += val;
-}
-
-class Autobianchi {
-  g() => super[0];
-}