ENH: externalize MapieClassifier methods into several non-conformity scores

[thibaultcordier]

Description

Outsource the MapieClassifier methods (LAC, APS, RAPS, TOPK) by extending the non-conformity score class to the classification task.

Fixes #467

Type of change

• 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?

• Test that existing code continues to work
• Test that the proposed solution can enable new non-conformity scores

Checklist

• I have read the contributing guidelines
• I have updated the HISTORY.rst and AUTHORS.rst files
• Linting passes successfully : make lint
• Typing passes successfully : make type-check
• Unit tests pass successfully : make tests
• Coverage is 100% : make coverage
• Documentation builds successfully : make doc

[vincentblot28]

What a tour de force @thibaultcordier !! Great improvement to the classification API !
General comment about the example: as in the future we prefer to use directly the conformity scores (and the argument "method" might be removed) I think examples should follow the new way of using MapieClassifier