Move kernel baseline tests to front_end.

pkg/front_end/testcases/rasta/super_operator.dart.dartk.expect

 library;
 import self as self;
 import "dart:core" as core;
 
 class A extends core::Object {
   constructor •() → self::A
     : super core::Object::•();
   operator +(core::String s) → dynamic
     return null;
   operator [](dynamic i) → dynamic
     return null;
   operator []=(dynamic i, dynamic val) → dynamic {}
 }
 class B extends self::A {
   constructor •() → self::B
     : super self::A::•();
   operator +(core::String s) → dynamic
     return super.{self::A::+}("${s}${s}");
   operator [](dynamic i) → dynamic
     return super.{self::A::[]}(i);
   operator []=(dynamic i, dynamic val) → dynamic
     return let final dynamic #t1 = let final dynamic #t2 = i in let final dynamic #t3 = i = #t2.+(1) in #t2 in let final dynamic #t4 = super.{self::A::[]}(#t1).+(val) in let final dynamic #t5 = super.{self::A::[]=}(#t1, #t4) in #t4;
 }
 class Autobianchi extends core::Object {
   constructor •() → self::Autobianchi
     : super core::Object::•();
   method g() → dynamic
     return super.[](0);
 }