Make prepare_split more robust if errors in metadata dataset_info splits
This PR uses `split_generator.split_info` as default value for `split_info` if any exception is raised while trying to get `split_generator.name` from `self.info.splits` (this may happen if there is any error in the metadata dataset_info splits).

Please note that `split_info` is only used by the logger.

Fix #5895 if passed `verification_mode="no_checks"`:
```python
ds = load_dataset(
    "ArmelR/stack-exchange-instruction", 
    data_dir="data/finetune", 
    split="train", 
    verification_mode="no_checks", 
    revision="c609f1caade5cfbf3b9fe9cfa17d7cb000b457bd",
)
```