refactor(agents): organise the agents package by what each module holds

- tools.py: the analysts' data tools, previously seven modules under utils
- context.py (was agent_utils, without its tool re-exports), state.py, rating.py and structured.py sit beside schemas.py
- every role package has an __init__

tests/test_instrument_identity.py

@@ -7,7 +7,7 @@ from unittest.mock import patch
 import pytest
 from langchain_core.messages import AIMessage, HumanMessage, RemoveMessage
 
-from tradingagents.agents.utils.agent_utils import (
+from tradingagents.agents.context import (
     build_instrument_context,
     create_msg_delete,
     get_instrument_context_from_state,