Compatibility with StateSpaceSets v2

[kahaaga]

This PR:

• Adds various fixes/tweaks for compatibility with StateSpaceSets.jl v2.
• Adds various fixes/tweaks for compatibility with ComplexityMeasures v3.X, which depended on the above point.
• Improved documentation strings for a few mutual info estimators.
• Increments minor version to 4.3 and adds a corresponding changelog entry.
• Adds more tests for OCE

The user-facing API is not changed in any way - only internals.

Closes #389.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.65%. Comparing base (27a2bb8) to head (0e845b1).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #392      +/-   ##
==========================================
- Coverage   94.94%   94.65%   -0.30%     
==========================================
  Files         111      111              
  Lines        3205     3198       -7     
==========================================
- Hits         3043     3027      -16     
- Misses        162      171       +9     

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