Qwen 2.5 Omni: apply video defaults
Author: pcuenca
Pull request: yes

# What does this PR do?

Applies `min_pixels` and `max_pixels` values to video processor.

The values were taken from [the original processing codebase](https://github.com/QwenLM/Qwen2.5-Omni/blob/7c8dddb38d52a58ce57e778e10fa0eaf26e078e9/qwen-omni-utils/src/qwen_omni_utils/v2_5/vision_process.py#L30), which uses a different set for [video](https://github.com/QwenLM/Qwen2.5-Omni/blob/7c8dddb38d52a58ce57e778e10fa0eaf26e078e9/qwen-omni-utils/src/qwen_omni_utils/v2_5/vision_process.py#L30) than it does for [images](https://github.com/QwenLM/Qwen2.5-Omni/blob/7c8dddb38d52a58ce57e778e10fa0eaf26e078e9/qwen-omni-utils/src/qwen_omni_utils/v2_5/vision_process.py#L26).

In our case, the image processor would always default to the image case, which results in frames resized to very large sizes, possibly causing OOMs, and preparing inputs with shapes not seen by the model during training.

## Reproduction

Consider the following snippet:

```py
import soundfile as sf
from transformers import Qwen2_5OmniForConditionalGeneration, Qwen2_5OmniProcessor

model_id = "Qwen/Qwen2.5-Omni-7B"
processor = Qwen2_5OmniProcessor.from_pretrained(model_id)

conversation = [
    {
        "role": "system",
        "content": [
            {"type": "text", "text": "You are Qwen, a virtual human developed by the Qwen Team, Alibaba Group, capable of perceiving auditory and visual inputs, as well as generating text and speech."}
        ],
    },
    {
        "role": "user",
        "content": [
             {"type": "video", "video": "https://qianwen-res.oss-cn-beijing.aliyuncs.com/Qwen2.5-Omni/draw.mp4"},
            {"type": "text", "text": "What can you hear and see in this video?"},
        ],
    },
]

inputs = processor.apply_chat_template(
    conversation,
    load_audio_from_video=True,
    add_generation_prompt=True,
    tokenize=True,
    return_dict=True,
    return_tensors="pt",
    video_fps=2,

    # kwargs to be passed to `Qwen2-5-OmniProcessor`
    padding=True,
    use_audio_in_video=True,
)

print(inputs["pixel_values_videos"].shape)
```

* Before this PR: `[886116, 1176]`
* After this PR: `[60480, 1176]`
* Reference, using qwen_omni_utils.process_mm_info: `[57600, 1176]`

The difference between this PR and the reference is because the original codebase selects `40` frames for this video, while we select `41`.

## Alternatives

* Use different config values for image and video processing and persist them to `preprocessor_config.json`.


Comments:
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I updated the tests to account for the new default sizes, let me know if this is ok to merge @zucchini-nlp! We can continue fps handling in #37687.

~~Question for @LysandreJik: should this be cherry-picked into the [preview release](https://github.com/huggingface/transformers/releases/tag/v4.51.3-Qwen2.5-Omni-preview)?~~ (As well as #37687 when it's ready)

It's already there, sorry.