Reorganize language/nonfunction_type_aliases/mixed/aliased_cyclic*

This test failed because it had a test outcome expectation comment in
a library which is not the entry point (cf. #44990). This CL changes
the test such that said comment is located in the entry point. The
trade-off is that this test now has a "reverse" import: A library
with null safety enabled imports a legacy library (but, apparently,
this does not cause the test to fail).

PS: This means that we don't have a test that will go green when #44990 is resolved.

Change-Id: Ie94bff22ce75bd662752c5814917e141fafc72ed
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/191365
Reviewed-by: Leaf Petersen <[email protected]>
Commit-Queue: Erik Ernst <[email protected]>

Author: eernstg

tests/language/nonfunction_type_aliases/mixed/aliased_cyclic_superclass_error_lib.dart

@@ -2,9 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-typedef T = C;
+import 'aliased_cyclic_superclass_error_test.dart';
 
-class C extends T {}
-//    ^
-// [analyzer] unspecified
-// [cfe] unspecified
+typedef T = C;

tests/language/nonfunction_type_aliases/mixed/aliased_cyclic_superclass_error_test.dart

@@ -11,4 +11,9 @@
 
 import 'aliased_cyclic_superclass_error_lib.dart';
 
+class C extends T {}
+//    ^
+// [analyzer] unspecified
+// [cfe] unspecified
+
 main() => C();