Add entropy, characteristic vector, and difference methods to SetPartition

[Potxssium]

###Authors

Guillaume Raschia - Polytech Nantes, LS2N
Alan Petit - Polytech Nantes
Théophile Tagne - Polytech Nantes

General description

This PR implements three new methods for the SetPartition class:

• entropy(base=2): Computes the Shannon entropy based on block sizes.
• characteristic_vector(): Returns the boolean vector of the equivalence relation (formerly assoc).
• diff(other): Returns blocks of self not contained in blocks of other.

###References

• diff: Based on the work of Hugo Dominguez (Polytech Nantes, 2021-2022) and the PhD Thesis of F. Dumonceaux (Nantes Université).
• entropy: C. E. Shannon (1948), "A Mathematical Theory of Communication". Computed on the block size distribution.
• characteristic_vector: Standard characteristic vector of the partition's equivalence relation (see W. M. Rand, 1971, JASA).

###Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the documentation preview.

Closes #41556