Revert to rescale and safely handle flag in owlvit config
# What does this PR do?

Reverts the `rescale_image` method name to back to `rescale`. This keeps the method inline with other method names such as `normalize`. 

This undoes the renaming in #18677 done to address failing tests caused by `rescale` key being in OWL-ViT config and the introduction of a `rescale` method in #18499. 

The OWL-ViT config has [since been updated](https://huggingface.co/google/owlvit-base-patch32/commit/17740e19dde58d657d21b970ead1cce0ea40f4da). As the model has been released, we rename the key in the config in case `rescale` is there for backwards compatibility. 


## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#start-contributing-pull-requests),
      Pull Request section?
- [ ] Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
      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
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?
_The documentation is not available anymore as the PR was closed or merged._