Faster sorting for single key items
### Feature request

A faster way to sort a dataset which contains a large number of rows.

### Motivation

The current sorting implementations took significantly longer than expected when I was running on a dataset trying to sort by timestamps. 

**Code snippet:**
```python
ds = datasets.load_dataset( "json", **{"data_files": {"train": "path-to-jsonlines"}, "split": "train"}, num_proc=os.cpu_count(), keep_in_memory=True) 
sorted_ds = ds.sort("pubDate", keep_in_memory=True)
```

However, once I switched to a different method which
1. unpacked to a list of tuples
2. sorted tuples by key
3. run `.select` with the sorted list of indices
It was significantly faster (orders of magnitude, especially with M's of rows)

### Your contribution

I'd be happy to implement a crude single key sorting algorithm so that other users can benefit from this trick. Broadly, this would take a `Dataset` and perform;

```python
# ds is a Dataset object
# key_name is the sorting key

class Dataset:
   ...
   def _sort(key_name: str) -> Dataset:
      index_keys = [(i,x) for i,x in enumerate(self[key_name])]
      sorted_rows = sorted(row_pubdate, key=lambda x: x[1])
      sorted_indicies = [x[0] for x in sorted_rows]
      return self.select(sorted_indicies)
```