[HfFileSystem] Faster fs.walk()

[lhoestq]

...by using expand_info=False by default (same logic as fs.glob())

before:

In [1]: from huggingface_hub import HfFileSystem

In [2]: %time _ = list(HfFileSystem().walk("hf://datasets/allenai/c4/en"))
CPU times: user 275 ms, sys: 27.6 ms, total: 302 ms
Wall time: 11.6 s

after:

In [1]: from huggingface_hub import HfFileSystem

In [2]: %time _ = list(HfFileSystem().walk("hf://datasets/allenai/c4/en"))
CPU times: user 176 ms, sys: 22.4 ms, total: 198 ms
Wall time: 3.25 s

[HuggingFaceDocBuilderDev]

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[Wauplin]

Looks good to me! Thanks @lhoestq for working on that :)