refactor: Enhance docs, code, add tests in `MaximumSumOfDistinctSubar…

[Hardvan]

…raysWithLengthK`

• 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 77.10%. Comparing base (c0ca704) to head (f270859).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #6649   +/-   ##
=========================================
  Coverage     77.10%   77.10%           
  Complexity     6110     6110           
=========================================
  Files           719      719           
  Lines         20437    20434    -3     
  Branches       3952     3950    -2     
=========================================
- Hits          15758    15756    -2     
  Misses         4080     4080           
+ Partials        599      598    -1     

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[DenizAltunkapan]

@Hardvan Please fix the failing workflows so I can start the review.