[HFFS] Hanlde "refs/convert/parquet" and "refs/pr/(\d)+" (PRs) revision correctly

[Wauplin]

Mentioned in #1707 (comment).

In HfFileSystem, revision with a "/" doesn't work properly if the / are not url-encoded properly.

Example

"hf://datasets/lambdalabs/pokemon-blip-captions@refs/convert/parquet/default/train/000.parquet"

is not a valid path to file ./default/train/000.parquet in revision refs/convert/parquet.

The correct path is

"hf://datasets/lambdalabs/pokemon-blip-captions@refs%2Fconvert%2Fparquet/default/train/000.parquet"

Since refs/convert/parquet is a quite special revision, let's handle it separately (same for PR revisions like refs/pr/1).

Note: this will make repos with a file refs/convert/parquet/default/train/000.parquet less convenient to request. However, this is very unlikely to happen compared to the normal use case of revision.

cc @mariosasko @Hakimovich99

[lhoestq]

Note that you can use the ~parquet alias:

dd.read_parquet("hf://datasets/jamescalam/llama-2-arxiv-papers-chunked@~parquet")

[Wauplin]

Resolved by #1712.