Support AgentExecutor features via create_agent_executor

[ccurme]

Privileged issue

• [X] I am a LangChain maintainer, or was asked directly by a LangChain maintainer to create an issue here.

Issue Content

• [x] ~max_iterations~ handled by recursion_limit config?
• [X] ~max_execution_time~ OK with step_timeout? (via asyncio task timeouts)
• [X] return_intermediate_steps (always)
• [X] trim_intermediate_steps (via the message functioN)
• [ ] handle_parsing_errors
• [ X] early_stopping_method (via timeouts + recursion error handling)
• [ X] verbose (via deug)
• [x] handle old style tools that do not expose a schema and expect a single string argument as an input
• [ ] ??