Support having multiple sub-processors (of any kind) in the same processor (#42667)
* support saving/loading multiple sub_processor of the same kind
* standardize all processors
* remove tokenizer_class from lasr
* fix modular
* fix kwargs logic
* override _load_tokenizer_from_pretrained in pixtral and fuyu
* fix missing subfolder loading primary tokenizer
* remove Fast suffix in tokenization auto
* revert to ParakeetTokenizerFast (not yet updated)
* Set TestMistralCommonBackend as flaky