Feat: Redesign and refactor agent module (#9113)

### What problem does this PR solve?

#9082 #6365

<u> **WARNING: it's not compatible with the older version of `Agent`
module, which means that `Agent` from older versions can not work
anymore.**</u>

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

api/apps/dialog_app.py

@@ -51,7 +51,7 @@ def set_dialog():
     vector_similarity_weight = req.get("vector_similarity_weight", 0.3)
     llm_setting = req.get("llm_setting", {})
     prompt_config = req["prompt_config"]
-    
+
     if not req.get("kb_ids", []) and not prompt_config.get("tavily_api_key") and "{knowledge}" in prompt_config['system']:
         return get_data_error_result(message="Please remove `{knowledge}` in system prompt since no knowledge base/Tavily used here.")