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     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[DenizAltunkapan]

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