Faster zero shot image
Author: Narsil
Pull request: yes

# What does this PR do?

Should superseed: https://github.com/huggingface/transformers/pull/21861#event-8644623666

- Keeps `batch_size` active, but restricts it to the `image`part.
- Calculates `candidate_labels` features only once (there's no way with this current pipeline to send different candidate_labels so we can take the optimization.
- Ultra narrowed for `CLIP` but the pipeline has existed for 4 months now with no new models. Given the popularity of CLIP for diffusion models, I think this is ok to overspecify. We can always relax later when new models come in.

This allows to downgrade from ChunkPipeline to regular PIpeline

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Comments:
@yessenzhar

_The documentation is not available anymore as the PR was closed or merged._

Does it also do a cross product ? Then possibly yes.

I mostly copy pasted the whole sequence. Will open a PR 

> I mostly copy pasted the whole sequence. Will open a PR

The cross product is in the model itself (image_batch_size x text_batch_size).

CLAP has the same implementation for loss and etc. So we should see a similar behaviour 


@Narsil Thank you for sorting this out this quick.