Move kernel baseline tests to front_end.

pkg/kernel/testcases/input/null_aware.dart

Index: pkg/kernel/testcases/input/null_aware.dart
diff --git a/pkg/kernel/testcases/input/null_aware.dart b/pkg/kernel/testcases/input/null_aware.dart
deleted file mode 100644
index bb1e3e0dd01346ec57ca7d3925e602b852ed08ac..0000000000000000000000000000000000000000
--- a/pkg/kernel/testcases/input/null_aware.dart
+++ /dev/null
@@ -1,20 +0,0 @@
-// 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 file.
-class Foo {
-  int field;
-  static int staticField;
-}
-
-main() {
-  Foo foo = new Foo();
-  foo?.field = 5;
-  Foo?.staticField = 5;
-  foo.field ??= 5;
-  Foo.staticField ??= 5;
-  foo?.field ??= 5;
-  Foo?.staticField ??= 5;
-
-  int intValue = foo.field ?? 6;
-  num numValue = foo.field ?? 4.5;
-}