Make IterableDataset (optionally) resumable
### What does this PR do?
This PR introduces a new `stateful` option to the `dataset.shuffle` method, which defaults to `False`. 
When enabled, this option allows for resumable shuffling of `IterableDataset` instances, albeit with some additional memory overhead.

Key points:
* All tests have passed
* Docstrings have been updated to reflect the new functionality

I'm very looking forward to receiving feedback on this implementation! @lhoestq