Pipeline VQA: Add support for list of images and questions as pipeline input
Author: ngvuhuy
Pull request: yes

# What does this PR do?

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Fixes #31216  

This PR will allow passing list of either `PIL.Image` or `str` as pipeline argument (and `list[str]` for questions). Passing dataset (in form of `.pt_utils.KeyDataset`) is also allowed.
So this code will now work (passing the dataset as list)
```python
from transformers import pipeline
dataset = datasets.load_dataset("frgfm/imagenette", "full_size", "validation[:10]")
oracle = pipeline(task="vqa", model="dandelin/vilt-b32-finetuned-vqa")
oracle(question="What's in this image?", image=dataset['image'], top_k=1)
```

This also works:
```python
from transformers.pipelines.pt_utls import KeyDataset

oracle(question="What's in this image?", image=KeyDataset(dataset, "image"), top_k=1)
```


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Comments:
Hi @amyeroberts, thank you for reviewing :) I added the tests and docstrings
As for the docstring, I assume you mean the comments inside the function? There isn't much to update there (the original author wrote the "correct" documentation, but did not implement everything for some reason). 

Found and fixed the problem with the dataset :) Now dataset (in form of `KeyDataset`, to stay consistent with [this tutorial](https://huggingface.co/docs/transformers/main/en/pipeline_tutorial#using-pipelines-on-a-dataset)) as input for image is accepted

Thanks again for this contribution!