Add thousands separator in training summary (#22583)

The logger prints a summary at the beginning of training that displays some info such as number of examples, number of parameters, total number of steps, etc. Those numbers can be quite large and difficult to read. I added a thousand separator to improve readability for the following:
- num_examples
- num_train_epochs
- per_device_train_batch_size
- total_train_batch_size
- max_steps
- num_trainable_params

src/transformers/trainer.py

@@ -1764,13 +1764,13 @@ class Trainer:
 
         # Train!
         logger.info("***** Running training *****")
-        logger.info(f"  Num examples = {num_examples}")
-        logger.info(f"  Num Epochs = {num_train_epochs}")
-        logger.info(f"  Instantaneous batch size per device = {args.per_device_train_batch_size}")
-        logger.info(f"  Total train batch size (w. parallel, distributed & accumulation) = {total_train_batch_size}")
+        logger.info(f"  Num examples = {num_examples:,}")
+        logger.info(f"  Num Epochs = {num_train_epochs:,}")
+        logger.info(f"  Instantaneous batch size per device = {args.per_device_train_batch_size:,}")
+        logger.info(f"  Total train batch size (w. parallel, distributed & accumulation) = {total_train_batch_size:,}")
         logger.info(f"  Gradient Accumulation steps = {args.gradient_accumulation_steps}")
-        logger.info(f"  Total optimization steps = {max_steps}")
-        logger.info(f"  Number of trainable parameters = {get_model_param_count(model, trainable_only=True)}")
+        logger.info(f"  Total optimization steps = {max_steps:,}")
+        logger.info(f"  Number of trainable parameters = {get_model_param_count(model, trainable_only=True):,}")
 
         self.state.epoch = 0
         start_time = time.time()