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 77.85%. Comparing base (e1773e9) to head (a3ad5ec).

Additional details and impacted files

@@ Coverage Diff @@ ## master #6649 +/- ## ========================================= Coverage 77.85% 77.85% Complexity 6359 6359 ========================================= Files 731 731 Lines 21190 21187 -3 Branches 4142 4140 -2 ========================================= - Hits 16497 16495 -2  Misses 4034 4034 + Partials 659 658 -1 

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[DenizAltunkapan]

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