Support WebDataset containing file basenames with dots
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_6888). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update. I think webdataset splits the file name and extension using the first dot no ?

https://github.com/webdataset/webdataset/blob/945b251a872ec0d337be8f9ea17a9c5b0d017ff3/webdataset/tariterators.py#L226

links to this function that splits on first dot

```python

def base_plus_ext(path):
    """Split off all file extensions.

    Returns base, allext.

    Args:
        path: path with extensions

    Returns:
        path with all extensions removed
    """
    match = re.match(r"^((?:.*/|)[^.]+)[.]([^/]*)$", path)
    if not match:
        return None, None
    return match.group(1), match.group(2)
``` So maybe the original issue is actually due to one of the files containing a dot in its file name that is not for the extension

```python
>>> base_plus_ext("15_Cohen_1-s2.0-S0929664620300449-gr3_lrg-b.png")
('15_Cohen_1-s2', '0-S0929664620300449-gr3_lrg-b.png')
``` Thanks for your review, @lhoestq.

I was not aware that `webdataset` requires filenames without dots in their basenames. I they can have dots for the extension (that becomes the column name) but not in the key used to group files into samples
Support WebDataset containing file basenames with dots.

Fix #6880.