dataset cache only stores one config of the dataset in parquet dir, and uses that for all other configs resulting in showing same data in all configs.
### Describe the bug

ds = load_dataset("ai2_arc", "ARC-Easy"), i have tried to force redownload, delete cache and changing the cache dir.

### Steps to reproduce the bug

dataset = []
dataset_name = "ai2_arc"
possible_configs = [
    'ARC-Challenge',
    'ARC-Easy'
    ]
for config in possible_configs:
    dataset_slice = load_dataset(dataset_name, config,ignore_verifications=True,cache_dir='ai2_arc_files')
    dataset.append(dataset_slice)

### Expected behavior

all configs should get saved in cache with their respective names.

### Environment info

ai2_arc