Add register method to AutoProcessor (#15669)
* Add push_to_hub method to processors
* Fix test
* The other one too!
* Add register method to AutoProcessor
* Update src/transformers/models/auto/processing_auto.py
Co-authored-by: Lysandre Debut <lysandre.debut@reseau.eseo.fr>
Co-authored-by: Lysandre Debut <lysandre.debut@reseau.eseo.fr>