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/eval.txt b/runtime/doc/eval.txt
index 4620623..1f52d9f 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -3022,6 +3022,8 @@
 test_garbagecollect_now()	none	free memory right now for testing
 test_garbagecollect_soon()	none	free memory soon for testing
 test_getvalue({string})		any	get value of an internal variable
+test_gui_mouse_event({button}, {row}, {col}, {repeated}, {mods})
+				none	add a mouse event to the input buffer
 test_ignore_error({expr})	none	ignore a specific error
 test_null_blob()		Blob	null value for testing
 test_null_channel()		Channel	null value for testing