feat: Add Hierholzer's Algorithm for Eulerian Circuits

[sairamsharan]

• 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

❌ Patch coverage is 76.56250% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.33%. Comparing base (0837424) to head (78d950c).

Files with missing lines	Patch %	Lines
...a/com/thealgorithms/graph/HierholzerAlgorithm.java	76.56%	5 Missing and 10 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6726      +/-   ##
============================================
- Coverage     78.34%   78.33%   -0.01%     
- Complexity     6621     6639      +18     
============================================
  Files           747      748       +1     
  Lines         22036    22100      +64     
  Branches       4322     4340      +18     
============================================
+ Hits          17264    17313      +49     
- Misses         4085     4090       +5     
- Partials        687      697      +10     

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[DenizAltunkapan]

@sairamsharan Thank you for your contribution. Please remove ChatGPT-like "FINAL FIX" comments.

[sairamsharan]

@DenizAltunkapan Just a quick reminder about this PR. I've addressed the previous comments and would appreciate it if you could take another look when you have a moment. Thanks!

[DenizAltunkapan]

thank you for your contribution @sairamsharan