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

docs/source/zh/quicktour.md

@@ -476,7 +476,7 @@ tensor([[0.0021, 0.0018, 0.0115, 0.2121, 0.7725],
 ...     args=training_args,
 ...     train_dataset=dataset["train"],
 ...     eval_dataset=dataset["test"],
-...     tokenizer=tokenizer,
+...     processing_class=tokenizer,
 ...     data_collator=data_collator,
 ... )  # doctest: +SKIP
 ```