DIscrete Optimization, Smooth Functional Maps, Bijective ZoomOut

[gviga]

This PR introduces three additional refinement methods from:
[1] MapTree: Recovering Multiple Solutions in the Space of Maps (https://arxiv.org/abs/2006.02532)
[2] Discrete Optimization for Shape Matching (https://www.lix.polytechnique.fr/~maks/papers/SGP21_DiscMapOpt.pdf)
[3] Smooth Non-Rigid Shape Matching via Effective Dirichlet Energy Optimization (https://arxiv.org/abs/2210.02870)

Some of these methods extend the conversion modules and refinement modules, needing to create a BijectiveItaretiveRefiner and other modifications of Converters.
[2] can be seen as a generalization of the ZoomOut algorithm. We could think to a redescign in which ZoomOut is a special instance of this algorithm. However, I think it would be cool to have also different implementations and then show that they are equivalent.

In general, we have to discuss whether the current structure of the converter (that takes a FM and return a p2p) can be extended to a common structure that can be used also when we want to input 2FM and return the two p2p in both directions, or it is better to create different converter classes for each purpose.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 84.06375% with 40 lines in your changes missing coverage. Please review.

Project coverage is 82.16%. Comparing base (680627e) to head (53ec33d).

Files with missing lines	Patch %	Lines
geomfum/refine.py	82.70%	23 Missing ⚠️
geomfum/convert.py	85.59%	17 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #37      +/-   ##
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+ Coverage   81.08%   82.16%   +1.08%     
==========================================
  Files          45       45              
  Lines        1385     1632     +247     
==========================================
+ Hits         1123     1341     +218     
- Misses        262      291      +29     

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