Add shared tests demonstrating bugs #25624, #25625, and #25626.

tests/language/accessor_conflict_setter.dart

Index: tests/language/accessor_conflict_setter.dart
diff --git a/pkg/analyzer_cli/test/data/package_with_embedder_yaml/lib/grizzly.dart b/tests/language/accessor_conflict_setter.dart
similarity index 81%
copy from pkg/analyzer_cli/test/data/package_with_embedder_yaml/lib/grizzly.dart
copy to tests/language/accessor_conflict_setter.dart
index d575643598c26036bc0e72a3592eeccc5d6eaf44..9dcf67d7f448386419e448aa547fb3b8818025a7 100644
--- a/pkg/analyzer_cli/test/data/package_with_embedder_yaml/lib/grizzly.dart
+++ b/tests/language/accessor_conflict_setter.dart
@@ -2,6 +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.
 
-library grizzly;
+var setValue;
 
-class Bear {}
+set x(value) { setValue = value; }