Add GCD implementation using Euclidean algorithm

[Swati89923]

Added a GCD implementation using the Euclidean algorithm along with unit tests.

• 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 similar explanations.
• All new algorithms include a corresponding test class that validates their functionality.
• All new code is formatted according to the project standards.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.92%. Comparing base (e945f16) to head (132dbd6).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7189      +/-   ##
============================================
+ Coverage     78.91%   78.92%   +0.01%     
- Complexity     6883     6886       +3     
============================================
  Files           774      775       +1     
  Lines         22746    22758      +12     
  Branches       4468     4471       +3     
============================================
+ Hits          17949    17962      +13     
+ Misses         4077     4076       -1     
  Partials        720      720              

☔ 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.

[Swati89923]

Hi maintainers 👋
Just checking in. Please let me know if any changes are needed from my side.
Thanks!