Feature/tests clean up

[michalk8]

Fix RNG re-use, remove old initialize methods.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 86.98%. Comparing base (26c0001) to head (b64575d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #706      +/-   ##
==========================================
+ Coverage   86.97%   86.98%   +0.01%     
==========================================
  Files          85       85              
  Lines        8888     8892       +4     
  Branches      616      616              
==========================================
+ Hits         7730     7735       +5     
  Misses        998      998              
+ Partials      160      159       -1     

Files with missing lines	Coverage Δ
src/ott/geometry/low_rank.py	96.40% <100.00%> (ø)
src/ott/math/matrix_square_root.py	100.00% <100.00%> (ø)
src/ott/neural/data/semidiscrete_dataloader.py	96.42% <100.00%> (ø)
src/ott/neural/methods/flow_matching.py	95.53% <100.00%> (+0.89%)	⬆️
src/ott/tools/gaussian_mixture/gaussian_mixture.py	94.57% <ø> (ø)
src/ott/tools/sliced.py	100.00% <100.00%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.