patch 8.2.3028: GUI mouse events not tested

Problem:    GUI mouse events not tested.
Solution:   Add test_gui_mouse_event().  Add mouse tests. Also add a few
            viminfo tests. (Yegappan Lakshmanan, closes #8407)
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index 09d5a39..de7f197 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -1021,6 +1021,7 @@
 	test_garbagecollect_now()   free memory right now
 	test_garbagecollect_soon()  set a flag to free memory soon
 	test_getvalue()		get value of an internal variable
+	test_gui_mouse_event()	add a GUI mouse event to the input buffer
 	test_ignore_error()	ignore a specific error message
 	test_null_blob()	return a null Blob
 	test_null_channel()	return a null Channel