Add support for nested images to LLava and VipLLava
Author: yonigozlan
Pull request: yes

# What does this PR do?

This PR adds the functions `make_flat_list_of_images` , `make_nested_list_of_images` and `make_batched_videos` to `image_utils`, removing some unnecessarily duplicated code.
`make_flat_list_of_images` also replaces make_list_of_images in clip, blip, and siglip image processors, as it allows image-text-to-text models which use these image processors to support nested images inputs, while preserving BC.

Partially addresses https://github.com/huggingface/transformers/issues/34545
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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_35558). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

Flagging this PR too - I made some changes to the Llava/Pixtral processing for nested images here, so there might be some conflicts! https://github.com/huggingface/transformers/pull/34801

Done! @ArthurZucker this is ready for review :) 

Hey @ArthurZucker If you have some bandwidth for a review, this PR would be a nice step towards uniformizing how we handle image/video processing