Move kernel baseline tests to front_end.

pkg/front_end/testcases/prefer_baseclass.dart.outline.expect

 library;
 import self as self;
 import "dart:core" as core;
 
 class A extends core::Object {
   constructor •() → void
-    : super core::Object::•()
     ;
 }
 class B extends core::Object {
   constructor •() → void
-    : super core::Object::•()
     ;
 }
 class AB1 extends self::A implements self::B {
   constructor •() → void
-    : super self::A::•()
     ;
 }
 class AB2 extends self::A implements self::B {
   constructor •() → void
-    : super self::A::•()
     ;
 }
 class BA1 extends self::B implements self::A {
   constructor •() → void
-    : super self::B::•()
     ;
 }
 class BA2 extends self::B implements self::A {
   constructor •() → void
-    : super self::B::•()
     ;
 }
-static method takeSubclassOfA(dynamic obj) → dynamic {}
-static method takeSubclassOfB(dynamic obj) → dynamic {}
-static method main() → dynamic {
-  self::takeSubclassOfA(new self::AB1::•());
-  self::takeSubclassOfA(new self::AB2::•());
-  self::takeSubclassOfB(new self::BA1::•());
-  self::takeSubclassOfB(new self::BA2::•());
-}
+static method takeSubclassOfA(dynamic obj) → dynamic
+  ;
+static method takeSubclassOfB(dynamic obj) → dynamic
+  ;
+static method main() → dynamic
+  ;