Add retry for preupload endpoint

[hanouticelina]

The /preupload/ endpoint is called in chunks of 256 files when uploading to the Hub. for large uploads, this means multiple sequential API calls, making it more likely to hit rate limits. Also, thanks to @Wauplin's dashboard (private link), we can see quite a lot of 429 errors on this endpoint in the last 24h.
let's take advantage of the rate limit header parsing to introduce smart retry handling. the PR also introduces backoff retry for transient errors (5xx).

[HuggingFaceDocBuilderDev]

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[Wauplin]

The /preupload/ endpoint is called in chunks of 256 files when uploading to the Hub. for large uploads, this means multiple sequential API calls, making it more likely to hit rate limits.

To complement on that, it is also possible in some workflows that the /preupload endpoint is called per-file. This is something we try to avoid but can't control it ourselves if users are doing it.

Anyway, agree we should mitigate HTTP 429 errors!