Add padding image transformation
# What does this PR do?

Adds padding to the image transforms library. 

## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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      Pull Request section?
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      to it if that's the case.
- [ ] Did you make sure to update the documentation with your changes? Here are the
      [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and
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- [x] Did you write any new necessary tests?
_The documentation is not available anymore as the PR was closed or merged._<|||||>The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_19838). All of your documentation changes will be reflected on that endpoint.<|||||>@NielsRogge I've asked for re-review as the logic has changed a bit from when you first reviewed. <|||||>> Thanks for adding! Do you think it'd be useful to add a pytorch padding vs our implementation equivalence test?

@NielsRogge What do you think should be covered wrt equivalence - is there logic you want to make sure is always aligned between the two? These transformations aren't meant to be a np copy of the torch library so there isn't a 1:1 mapping. <|||||>@NielsRogge I'm going to merge. If we decide to add the equivalence tests I'll add in a follow up PR. <|||||>Ok fine, it's just that I was working on a model (#19784) that leverages torch.nn.functional.pad as seen [here](https://github.com/mv-lab/swin2sr/blob/7eeebfba849bbc934ea254ec4cfa8e9d6fc0672c/models/network_swin2sr.py#L891). So it'd be nice to check equivalence between PyTorch and our NumPy implementation.