Save nparray as list
### Describe the bug

When I use the `map` function to convert images into features, datasets saves nparray as a list. Some people use the `set_format` function to convert the column back, but doesn't this lose precision?

### Steps to reproduce the bug

the map function
```python
def convert_image_to_features(inst, processor, image_dir):
    image_file = inst["image_url"]
    file = image_file.split("/")[-1]
    image_path = os.path.join(image_dir, file)
    image = Image.open(image_path)
    image = image.convert("RGBA")

    inst["pixel_values"] = processor(images=image, return_tensors="np")["pixel_values"]
    return inst
```

main function
```python
map_fun = partial(
      convert_image_to_features, processor=processor, image_dir=image_dir
  )
ds = ds.map(map_fun, batched=False, num_proc=20)
print(type(ds[0]["pixel_values"])
```

### Expected behavior

(type < list>) 

### Environment info

- `datasets` version: 2.16.1
- Platform: Linux-4.19.91-009.ali4000.alios7.x86_64-x86_64-with-glibc2.35
- Python version: 3.11.5
- `huggingface_hub` version: 0.23.4
- PyArrow version: 14.0.2
- Pandas version: 2.1.4
- `fsspec` version: 2023.10.0