Feature/refactor relative epsilon

[michalk8]

@marcocuturi could you please update the documentation?

closes #478

[codecov]

Codecov Report

Attention: Patch coverage is 94.44444% with 3 lines in your changes missing coverage. Please review.

Project coverage is 88.15%. Comparing base (561adbb) to head (d0e250f).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ott/geometry/geometry.py	92.85%	1 Missing and 1 partial ⚠️
src/ott/geometry/epsilon_scheduler.py	94.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #602      +/-   ##
==========================================
- Coverage   88.16%   88.15%   -0.01%     
==========================================
  Files          74       74              
  Lines        7764     7753      -11     
  Branches      544      542       -2     
==========================================
- Hits         6845     6835      -10     
+ Misses        778      777       -1     
  Partials      141      141              

Files with missing lines	Coverage Δ
src/ott/experimental/mmsinkhorn.py	91.56% <100.00%> (ø)
src/ott/geometry/grid.py	96.26% <100.00%> (+0.02%)	⬆️
src/ott/geometry/low_rank.py	96.73% <100.00%> (ø)
src/ott/geometry/pointcloud.py	95.43% <100.00%> (+0.02%)	⬆️
src/ott/initializers/quadratic/initializers.py	81.13% <100.00%> (ø)
src/ott/neural/methods/monge_gap.py	91.20% <ø> (ø)
src/ott/problems/quadratic/quadratic_problem.py	81.92% <ø> (ø)
src/ott/solvers/linear/discrete_barycenter.py	87.62% <100.00%> (ø)
src/ott/solvers/quadratic/gromov_wasserstein.py	88.98% <ø> (ø)
src/ott/geometry/epsilon_scheduler.py	95.83% <94.11%> (+1.38%)	⬆️
... and 1 more

[marcocuturi]

This is really nice.. and finally solves a longstanding ugly bug!!!

LGTM