[fix] Add DeformableDetrFeatureExtractor
# What does this PR do?

As pointed out by @Deppmeng who is adding Conditional DETR in #18948, the postprocessing of Deformable DETR is actually different compared to regular DETR. Namely, a sigmoid activation function is used rather than softmax, and the no-object class is included, whereas DETR discards this class.

Hence, we'll need a new `DeformableDetrFeatureExtractor` which includes this custom postprocessing logic. As only the postprocessing of object detection is different, I'm using `Copied from` statements wherever possible.

To do:

- [x] update `preprocessor_config.json` of all repos on the hub
- [x] use `from_pretrained` in the code snippets for the feature extractor
_The documentation is not available anymore as the PR was closed or merged._