Force ICNN to adopt default initialization of its own layers

[Algue-Rythme]

The ICNN used to rely on initialisation with normal matrices. Now, it fallbacks to the behavior of the layers, i.e lecun_normal, which scales the standard deviation of the weights with 1/sqrt(fan_in). This std is much smaller for wide networks.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.39%. Comparing base (787d4a9) to head (27c582a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #551      +/-   ##
==========================================
+ Coverage   91.38%   91.39%   +0.01%     
==========================================
  Files          69       69              
  Lines        7242     7242              
  Branches     1019     1018       -1     
==========================================
+ Hits         6618     6619       +1     
  Misses        472      472              
+ Partials      152      151       -1     

Files	Coverage Δ
src/ott/neural/networks/icnn.py	94.54% <100.00%> (ø)

... and 1 file with indirect coverage changes

[michalk8]

Thanks @Algue-Rythme , LGTM !