Feature/refactor initializers

[michalk8]

closes #591

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Codecov Report

Attention: Patch coverage is 86.79245% with 7 lines in your changes missing coverage. Please review.

Project coverage is 88.19%. Comparing base (b479e5f) to head (997ff18).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ott/initializers/quadratic/initializers.py	71.42%	2 Missing ⚠️
src/ott/tools/progot.py	33.33%	2 Missing ⚠️
src/ott/initializers/linear/initializers_lr.py	80.00%	1 Missing ⚠️
src/ott/solvers/linear/sinkhorn_lr.py	80.00%	0 Missing and 1 partial ⚠️
src/ott/solvers/quadratic/gromov_wasserstein_lr.py	80.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #599      +/-   ##
==========================================
- Coverage   88.23%   88.19%   -0.04%     
==========================================
  Files          74       74              
  Lines        7808     7760      -48     
  Branches      556      544      -12     
==========================================
- Hits         6889     6844      -45     
+ Misses        778      775       -3     
  Partials      141      141              

Files with missing lines	Coverage Δ
src/ott/initializers/linear/initializers.py	100.00% <100.00%> (ø)
src/ott/initializers/neural/meta_initializer.py	92.53% <100.00%> (+0.11%)	⬆️
src/ott/solvers/linear/sinkhorn.py	99.35% <100.00%> (-0.03%)	⬇️
src/ott/solvers/quadratic/gromov_wasserstein.py	88.98% <100.00%> (+0.55%)	⬆️
src/ott/tools/soft_sort.py	96.10% <100.00%> (+0.02%)	⬆️
src/ott/initializers/linear/initializers_lr.py	91.19% <80.00%> (-0.20%)	⬇️
src/ott/solvers/linear/sinkhorn_lr.py	98.61% <80.00%> (-0.37%)	⬇️
src/ott/solvers/quadratic/gromov_wasserstein_lr.py	80.96% <80.00%> (+0.25%)	⬆️
src/ott/initializers/quadratic/initializers.py	81.13% <71.42%> (-0.35%)	⬇️
src/ott/tools/progot.py	29.16% <33.33%> (ø)

[marcocuturi]

LGTM! thanks a lot @michalk8 for this refactoring