Increase speed of data files resolution
Certain datasets like `bigcode/the-stack-dedup` have so many files that loading them takes forever right from the data files resolution step.

`datasets` uses file patterns to check the structure of the repository but it takes too much time to iterate over and over again on all the data files.

This come from `resolve_patterns_in_dataset_repository` which calls `_resolve_single_pattern_in_dataset_repository`, which iterates on all the files at
```python
glob_iter = [PurePath(filepath) for filepath in fs.glob(PurePath(pattern).as_posix()) if fs.isfile(filepath)]
```
but calling `glob` on such a dataset is too expensive. Indeed it calls `ls()` in `hffilesystem.py` too many times.

Maybe `glob` can be more optimized in `hffilesystem.py`, or the data files resolution can directly be implemented in the filesystem by checking its `dir_cache` ?