Make training args fully immutable (#25435)

* Make training args fully immutable

* Working tests, PyTorch

* In test_trainer

* during testing

* Use proper dataclass way

* Fix test

* Another one

* Fix tf

* Lingering slow

* Exception

* Clean

tests/trainer/test_trainer.py

@@ -139,9 +139,9 @@ class RegressionTrainingArguments(TrainingArguments):
     b: float = 0.0
 
     def __post_init__(self):
-        super().__post_init__()
         # save resources not dealing with reporting (also avoids the warning when it's not set)
         self.report_to = []
+        super().__post_init__()
 
 
 class RepeatDataset:
@@ -529,7 +529,8 @@ class TrainerIntegrationPrerunTest(TestCasePlus, TrainerIntegrationCommon):
         self.check_trained_model(trainer.model)
 
         # Re-training should restart from scratch, thus lead the same results and new seed should be used.
-        trainer.args.seed = 314
+        args = TrainingArguments("./regression", learning_rate=0.1, seed=314)
+        trainer = Trainer(args=args, train_dataset=train_dataset, model_init=lambda: RegressionModel())
         trainer.train()
         self.check_trained_model(trainer.model, alternate_seed=True)