Fixes for GTShapley and scorers

[mdbenito]

Warning

This PR must be merged after #265

Description

This PR revolves around fixes for Group Testing Shapley. PR #267 will add some missing tests (e.g. Scorer)

Changes

• Introduces utils/score.py and the Scorer type to include information about range and default values when using compose_score. This is need e.g. for Group Testing, where an accurate range is necessary.
• Adds a missing argument to GTS
• Switches the default solver to cvxpy's SCS because scipy linprog's highs would fail to find solutions in the presence of outlier data.
• Removes the dedicated file test_gt.py and adds more tests using group testing.
• Closes Owen does not return proper status #263.

Checklist

• Wrote Unit tests (if necessary)
• Updated Documentation (if necessary)
• Updated Changelog
• If notebooks were added/changed, added boilerplate cells are tagged with "nbsphinx":"hidden"

[mdbenito]

@AnesBenmerzoug I'm afraid there is an error here that I fixed in #267 and the checks will keep failing. I would merge both in succession

[AnesBenmerzoug]

Other than the one comment and one question that I left, this looks good to me and could be merged as is.