Modifications:
- Do not mask the first turn in the chat history when `mask_history`.
- Preserve the original order of messages (do not reverse the list).

- Addresses occasional deadlocks in multi-threaded model server requests.
- Implemented a single-threaded, single-server setup for testing purposes.
- Observed that the Reward model's performance is acceptable and can be used.
- Temporarily adopting this single-threaded version

 step1: evaluate_code Change imap_unordered back to tqmd's process_map. Pool creates daemon processes, non-daemon processes can create new processes.