refactor: formalize artifact saving

[gsprochette]

Description

Formalize artifact saving and expose it to more algorithms, and add artifact hooks into Smash config

• Generalized artifact saving/loading: Extracted and formalized the artifact-saving logic so it is no longer tied specifically to the Torch Compile workflow. Other Pruna algorithms can now register and reuse the same standardized artifact save/load utilities.
• Config-driven hooks: Extended the Smash configuration to include save_artifacts_fns and load_artifacts_fns, working in a way similar to save_fns and load_fns
• Improved composability: This structure makes it easy to save artifacts (such as parameters estimated from a warmup, or checkpoints for finetuning or distillation).

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Additional Notes

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[llcnt]

Nice work, this is a very cool feature :) (I was personally doing a custom save/load artifacts in my ongoing PR )

[simlang]

looks good! Thanks for taking care of that, super useful for literally everything 🚀

Just had a question about the backward compatibility

[github-actions]

This PR has been inactive for 10 days and is now marked as stale.

[gsprochette]

@simlang in response to your comment I removed the logic in save.py and added this function:

• update both the save and load fns
• save the smash config so that it's fixed for when we remove this logic in a future version after some deprecation time
• log a warning saying it was updated and asking to warn any remote provider (because those would never receive the warning nor have the update automatically saved)

Let me know if that's to your liking