Add IFBench

[clefourrier]

This PR does 2 things:

1. add IFBench (process of comparing the numbers with the paper ongoing)
2. refacto the registry to make it simpler

• the successive functions which must be called in a specific order are now called in the init, functions have also been merged to make the flow easier
• the registry stores the configs once
• last but not least, the registry no longer tries to load all functions (including multilingual and extended and community), but uses the suites requested in the kwargs to know which to try.

[clefourrier]

in community tasks, changes are unrelated, it's just a bug fix

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[clefourrier]

Ok good to review, sorry about the monster PR

[clefourrier]

All the tasks edit are removing the truncating few shots, since it's no longer used

[clefourrier]

Main question at this point @NathanHB is : do you want me to split the registry edit into its own PR, and put ifbench in another one?