[FIX] Make ReliefF and RReliefF results replicable

[markotoplak]

Issue

ReliefF and RReliefF had default random_seed set to None. Therefore their results in Rank and Preprocess widgets could differ. I became aware of this when reviewing #7023.

Description of changes

I just changed the default random_seed, so now ReliefF is replicable unless explicitly specified not to be.

It would be trivial to add random_seed arguments in some places, but the Rank and Preprocess would need slightly bigger refactoring, because the current code there does not allow easy adding of arguments to various scorers.

Includes

• Code changes
• Tests
• Documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.36%. Comparing base (e67650f) to head (041ff6d).
Report is 42 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7026      +/-   ##
==========================================
- Coverage   88.36%   88.36%   -0.01%     
==========================================
  Files         332      332              
  Lines       73345    73345              
==========================================
- Hits        64814    64812       -2     
- Misses       8531     8533       +2     

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