Refactor Classwise Shapley

[AnesBenmerzoug]

Description

This PR refactors the Classwise Shapley valuation to be more aligned with the new Valuation classes.

Changes

• Implemented Classwise Scorer
• Implemented Classwise Sampler
• Implemented Classwise Utility
• Implemented Classwise Shapley valuation method
• Added with_idx and with_subset methods to Sample class.
• Added tests for the new classwise shapley method and a test that compares its output with the old implementation.

Checklist

• [X] Wrote Unit tests (if necessary)
• [ ] ~Updated Documentation (if necessary)~
• [ ] Updated Changelog
• [ ] ~If notebooks were added/changed, added boilerplate cells are tagged with "tags": ["hide"] or "tags": ["hide-input"]~

[AnesBenmerzoug]

@schroedk I resolved as many issues as possible but there is still one test that fails for some unknown reason and I am giving up on it. The test in question relies on non-default behaviour, i.e., it does not normalize the values after the valuation. The original paper's implementation normalizes the values and for that case the test passes.

[schroedk]

@schroedk I resolved as many issues as possible but there is still one test that fails for some unknown reason and I am giving up on it. The test in question relies on non-default behaviour, i.e., it does not normalize the values after the valuation. The original paper's implementation normalizes the values and for that case the test passes.

@AnesBenmerzoug the test is also failing on #558. Let's go for merging this branch and then iterate on #558. What is missing before we can merge this one?

[AnesBenmerzoug]

@schroedk the test I was talking about is specific to classwise shapley. I have no idea about that other test that is failing.

I think this PR can now be merged.