Logging Revamp

[hynky1999]

What does this implement/fix? Explain your changes.

This PR revamps output saving system.

• Adds fsspec support for output directory
• Fixes bug as the save_details parameter was never used or passed (now it's used)
• Since one can now directly push results/details to hub, I reduce the push_x_to_hub to just push_hub, which behaves just like the push_details_to_hub was working before
• Fixes the task_name extraction so that it doesn't explode once we move to year 2025 🫠
• Adds some tests for checking that the evaluation results are saved correctly, I ommited tests for tensorbard logging as I haven't changed anything there
  Comments

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• The tests now require HF_TOKEN, which can write/read in lighteval-tests. I have created org I can give the ownership to either @clefourrier or @NathanHB.
• Having secrets accessible during tests is big security risk especially when the tests can run without any interaction on PRs, but if the token has only permission to the lighteval-tests org I think it's fine
• We should probably first merge a PR which gives ownership to lighteval over the lighteval config. Right now I can adjust the config for lighteval for nanotron path to reflect the new api. You can review the PR in the meantime but I added todo, so that we don't forget that. PS: That PR doesn't exist yet.

[NathanHB]

Why did you remove this one ? There is a check at init that fails if this is not set while push_to_hub is set

[hynky1999]

I didn't remove it, I changed the ordering for some reason (during dev). We can move it up for sure.

[NathanHB]

Mhh I added it back a minute ago, I could'nt see it before

[hynky1999]

Ahh, actually indeed you are right, I was looking at the most recent diff and thought I changed that.
Should have done the tests properly so that this is catched (https://github.com/huggingface/lighteval/pull/284/files#diff-97ad1010a3f9d0568387464594c6396718637ed66d355d6b3280aa1f72607ba1R121). Will change it!

[hynky1999]

@NathanHB I will update this once #285 is merged to have use the new logging api