fix: guard optimize_refine_core against float32 noise oscillation

[yzhuang-els]

Fix #592

Modifications:

• add tol_optimization parameter to optimize_refine_core and require delta_local > tol_optimization for a move, instead of delta_local > 0
• thread Leiden.tol_optimization (default 1e-3, already exposed on the Python class) through to optimize_refine_core

Impacted submodules:

• sknetwork.clustering

This pull request:

• targets the develop branch
• does not decrease code coverage
• passes the tests
• is documented and the documentation build passes
• has PEP8-compliant code and explicit variable naming

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.22%. Comparing base (d16f81a) to head (241593b).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #593   +/-   ##
========================================
  Coverage    98.22%   98.22%           
========================================
  Files          182      182           
  Lines         8356     8356           
========================================
  Hits          8208     8208           
  Misses         148      148           

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