Implement heuristic cutting on the accessibility tree to get the important nodes; Finish accessibility tree text agent

mm_agents/gpt_4_prompt_code.py

@@ -11,7 +11,7 @@ You ONLY need to return the code inside a code block, like this:
 ```
 Specially, it is also allowed to return the following special code:
 When you think you have to wait for some time, return ```WAIT```;
-When you think the task can not be done, return ```FAIL```;
+When you think the task can not be done, return ```FAIL```, don't easily say ```FAIL```, try your best to do the task;
 When you think the task is done, return ```DONE```.
 
 First give the current screenshot and previous things we did a reflection, then RETURN ME THE CODE OR SPECIAL CODE I ASKED FOR. NEVER EVER RETURN ME ANYTHING ELSE.