[DX fix] Fixing QA pipeline streaming a dataset.
Author: Narsil
Pull request: yes

# What does this PR do?


Linked to https://github.com/huggingface/transformers/issues/18510
Enabling nicer code.

The dataset example of the docs : https://huggingface.co/docs/transformers/pipeline_tutorial#audio-pipeline

Wouldn't work as nicely on QA because of `QuestionAnsweringArgumentHandler`.

This handler is legacy and would iterate over the whole dataset
effectively killing all properties of the pipeline.
This restores nice properties when using `Dataset` or `Generator` since
those are meant to be consumed lazily. It means that neither `Dataset` nor `Generator` can contain odd input shapes like 
List of questions and single context, or lists of questions and list of contexts, but in general that should be OK since it is not advertised as working anywhere.


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Fixes # (issue)


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Comments:
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