Trainer - deprecate tokenizer for processing_class (#32385)

* Trainer - deprecate tokenizer for processing_class

* Extend chage across Seq2Seq trainer and docs

* Add tests

* Update to FutureWarning and add deprecation version

examples/pytorch/question-answering/run_qa.py

@@ -640,7 +640,7 @@ def main():
         train_dataset=train_dataset if training_args.do_train else None,
         eval_dataset=eval_dataset if training_args.do_eval else None,
         eval_examples=eval_examples if training_args.do_eval else None,
-        tokenizer=tokenizer,
+        processing_class=tokenizer,
         data_collator=data_collator,
         post_process_function=post_processing_function,
         compute_metrics=compute_metrics,

examples/pytorch/question-answering/run_qa_beam_search.py

@@ -666,7 +666,7 @@ def main():
         train_dataset=train_dataset if training_args.do_train else None,
         eval_dataset=eval_dataset if training_args.do_eval else None,
         eval_examples=eval_examples if training_args.do_eval else None,
-        tokenizer=tokenizer,
+        processing_class=tokenizer,
         data_collator=data_collator,
         post_process_function=post_processing_function,
         compute_metrics=compute_metrics,

examples/pytorch/question-answering/run_seq2seq_qa.py

@@ -663,7 +663,7 @@ def main():
         train_dataset=train_dataset if training_args.do_train else None,
         eval_dataset=eval_dataset if training_args.do_eval else None,
         eval_examples=eval_examples if training_args.do_eval else None,
-        tokenizer=tokenizer,
+        processing_class=tokenizer,
         data_collator=data_collator,
         compute_metrics=compute_metrics if training_args.predict_with_generate else None,
         post_process_function=post_processing_function,