Get an IterableDataset from a map-style Dataset
I think `stream` could be misleading since the data is not being streamed from remote endpoints (one could think that's the case when they see `load_dataset` followed by `stream`). Hence, I prefer the second option.

PS: When we resolve https://github.com/huggingface/datasets/issues/4542, we could add `as_tf_dataset` to the API for consistency and deprecate `to_tf_dataset`.
This is useful to leverage iterable datasets specific features like:
- fast approximate shuffling
- lazy map, filter etc.

Iterating over the resulting iterable dataset should be at least as fast at iterating over the map-style dataset.

Here are some ideas regarding the API:
```python
# 1. 
# - consistency with load_dataset(..., streaming=True)
# - gives intuition that map/filter/etc. are done on-the-fly
ids = ds.stream()

# 2.
# - more explicit on the output type
# - but maybe sounds like a conversion tool rather than a step in a processing pipeline
ids = ds.as_iterable_dataset()
```