HunyuanVideo: Add missing features (negative prompt and LLM template)

### Feature Idea

I would like to switch from ComfyUI-HunyuanVideoWrapper to the standard ComfyUI nodes BUT there are two missing features:
1. The ability to use **negative prompts** (this works well in the wrapper)
2. The ability to **disable HunyuanVideo's LLM** used to edit prompts (or change the prompt template but I don't use that).
Both of these features give total control of the video generation.

### Existing Solutions

Unless I'm mistaken, there doesn't seem to be any way except to use the ComfyUI-HunyuanVideoWrapper but I can't take advantage of other custom nodes then.

### Other

_No response_