Langroid

Minor type sig change

Upgrade to latest DuckDuckGoSearch

Groq support. For any model <m> hosted on `groq`, you can use it similar to how you'd use `ollama`, e.g.
`chat_model = "groq/llama3-8b-8192"`.
See the groq section here: https://langroid.github.io/langroid/tutorials/local-llm-setup/

New param in `Task.run(), Task.run_asyn()`: `session_id` which is used as a key to look up various settings in Redis cache.
Currently only used to look up "kill status" - this allows killing a running task, either by `task.kill()`
or by the classmethod `Task.kill_session(session_id)`

For example usage, see the `test_task_kill` in [`tests/main/test_task.py`](https://github.com/langroid/langroid/blob/main/tests/main/test_task.py)

TableChatAgent - For safety, enforce single pandas expression, not multiple lines of arbitrary code

* `Task.run()`, `run_batch_tasks()`, `run_batch_task_gen()` take an additional param (similar to `max_cost`): `max_tokens`. This is useful to control
runaway loops when using local LLMs
* `DocChatAgentConfig` has a new config param: `rerank_after_adding_context` to control whether we rerank before or after adding neighbor chunks.