refactor: Enhance docs, code, add tests in KrishnaMurthyNumber

[Hardvan]

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.19%. Comparing base (9a907c8) to head (77b6369).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6742      +/-   ##
============================================
+ Coverage     77.12%   77.19%   +0.06%     
+ Complexity     6119     6118       -1     
============================================
  Files           720      719       -1     
  Lines         20471    20452      -19     
  Branches       3961     3956       -5     
============================================
- Hits          15789    15787       -2     
+ Misses         4081     4063      -18     
- Partials        601      602       +1     

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[DenizAltunkapan]

Very helpful. Thank you @Hardvan