Fix non-function calls messages

[enyst]

End-user friendly description of the problem this fixes or functionality that this introduces

• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below
• fix 400 error on HuggingFace models
• fix KeyError on multiple LLMs

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Give a summary of what the PR does, explaining any non-trivial design decisions

This PR proposes a refactoring of Messages and function calling. It will fix the LLMs without function calling enabled:

• 400 error on HF for top_p=1
• 'content' error on many LLMs
• serialization of tool-like messages
• misc

HF model example that works:

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Link of any specific issues this addresses
Fix #4960
Fix #5090
Fix #5142

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To run this PR locally, use the following command:

docker run -it --rm   -p 3000:3000   -v /var/run/docker.sock:/var/run/docker.sock   --add-host host.docker.internal:host-gateway   -e SANDBOX_RUNTIME_CONTAINER_IMAGE=docker.all-hands.dev/all-hands-ai/runtime:f6e70f5-nikolaik   --name openhands-app-f6e70f5   docker.all-hands.dev/all-hands-ai/openhands:f6e70f5

[xingyaoww]

Except for some concern in adding function_calling_enabled -- otherwise LGTM!

[xingyaoww]

This will only be True for the selected set of model -- but we still send messages WITH tool_ids to the LLM

[enyst]

Ahh so we need the part of the serializer that adds tool_call_id. OK, sure, I'll revert that. Sigh, this is messy. The attempt to separate things when function calling is native is because we need to send a single thing, not a list.

(I'll follow up on litellm too, they actually do this kind of conversion, so we don't have to play whack-a-mole anymore)

[enyst]

@xingyaoww I actually restored this check, but it does send tool ids now. It just sends them as string, if non-native function calling, and as list if native. (because this applies now)

I started to work on refactoring the Message class. I think it needs to include tool calls/ids conversion part (at least as a single Message), do full serialization, and become closer to litellm's Message. I started to work on it on this branch, but in the meantime, I found out that people rely on this PR, and use it via docker because it solves what's broken with non-native function calling.

So I'll make another branch to work on the refactoring, and this PR is up for review again. If it's not too terrible, I'd say let's just fix the problems first, and refactor later.

(I'll clean up some leftover comment, too, but I prefer to do it if it's approved, because I think it would again break people's use via docker on the last commit.)

[neubig]

Updated the comment to note this fixes Fix #5142

[xingyaoww]

LGTM! Thanks!