Move kernel baseline tests to front_end.

pkg/front_end/test/fasta/mixin.dart.outline.expect

-library;
-import self as self;
-import "dart:core" as core;
-
-class B extends self::Object&M1&M2 {
-  constructor •(dynamic value) → void
-    ;
-}
-abstract class M1 extends core::Object {
-  constructor •() → void
-    ;
-  method m() → dynamic
-    ;
-}
-abstract class M2 extends core::Object {
-  constructor •() → void
-    ;
-  method m() → dynamic
-    ;
-}
-class C extends self::Object&M1&M2 {
-  constructor •(dynamic value) → void
-    ;
-}
-abstract class G1<T extends core::Object> extends core::Object {
-  constructor •() → void
-    ;
-  method m() → dynamic
-    ;
-}
-class D<S extends core::Object> extends self::D^G1<self::D::S> {
-  constructor •() → void
-    ;
-}
-abstract class Object&M1 = core::Object with self::M1 {
-}
-abstract class Object&M1&M2 = self::Object&M1 with self::M2 {
-}
-abstract class D^G1<S extends core::Object> = core::Object with self::G1<self::D^G1::S> {
-}
-static method main() → dynamic
-  ;