Process inputs directly in apply_chat_template in image-text-to-text pipeline
Author: yonigozlan
Pull request: yes

# What does this PR do?
Follows https://github.com/huggingface/transformers/pull/34275
Process inputs directly in `apply_chat_template` instead of calling `apply_chat_template` then the processor.
This also means that a small part of the pipeline logic needed to change, but I think it's better now :).
The pipeline also supports passing images with the `images` arg even when using chat template, where the corresponding image is represented with a `{"type": "image"}`  in the chat.

In the previous behavior, when the input was:
```py
image_ny = "https://cdn.britannica.com/61/93061-050-99147DCE/Statue-of-Liberty-Island-New-York-Bay.jpg"
image_chicago = "https://cdn.britannica.com/59/94459-050-DBA42467/Skyline-Chicago.jpg"
messages = [
    {
        "role": "user",
        "content": [
            {"type": "text", "text": "What’s the difference between these two images?"},
            {"type": "image"},
            {"type": "image"},
        ],
    }
]
outputs = pipe([image_ny, image_chicago], text=messages)
```
The output would be:
```py
[
    {
        "input_text": [
            {
                "role": "user",
                "content": [
                    {"type": "text", "text": "What’s the difference between these two images?"},
                    {"type": "image"},
                    {"type": "image"},
                ],
            }
        ],
        "generated_text": [
            {
                "role": "user",
                "content": [
                    {"type": "text", "text": "What’s the difference between these two images?"},
                    {"type": "image"},
                    {"type": "image"},
                ],
            },
            {
                "role": "assistant",
                "content": "The first image shows a statue of Liberty in the foreground, while the second image shows a city skyline",
            },
        ],
    }
]
```

With no mention of the actual input images.
Now the output is:

```py
[
    {
        "input_text": [
            {
                "role": "user",
                "content": [
                    {"type": "text", "text": "What’s the difference between these two images?"},
                    {
                        "type": "image",
                        "image": "https://cdn.britannica.com/61/93061-050-99147DCE/Statue-of-Liberty-Island-New-York-Bay.jpg",
                    },
                    {
                        "type": "image",
                        "image": "https://cdn.britannica.com/59/94459-050-DBA42467/Skyline-Chicago.jpg",
                    },
                ],
            }
        ],
        "generated_text": [
            {
                "role": "user",
                "content": [
                    {"type": "text", "text": "What’s the difference between these two images?"},
                    {
                        "type": "image",
                        "image": "https://cdn.britannica.com/61/93061-050-99147DCE/Statue-of-Liberty-Island-New-York-Bay.jpg",
                    },
                    {
                        "type": "image",
                        "image": "https://cdn.britannica.com/59/94459-050-DBA42467/Skyline-Chicago.jpg",
                    },
                ],
            },
            {
                "role": "assistant",
                "content": "The first image shows a statue of Liberty in the foreground, while the second image shows a city skyline",
            },
        ],
    }
]
```

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Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_35616). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

Added some docs and updated the branch, this should be ready to merge @ArthurZucker