Hierholzer algorithm

[quantambites]

• 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 72.72727% with 30 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.83%. Comparing base (4858ec9) to head (0a65994).

Files with missing lines	Patch %	Lines
...om/thealgorithms/graph/HierholzerEulerianPath.java	72.72%	17 Missing and 13 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6820      +/-   ##
============================================
- Coverage     77.85%   77.83%   -0.03%     
- Complexity     6359     6383      +24     
============================================
  Files           731      732       +1     
  Lines         21187    21297     +110     
  Branches       4140     4178      +38     
============================================
+ Hits          16495    16576      +81     
- Misses         4034     4050      +16     
- Partials        658      671      +13     

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