refactor: Enhance docs, add tests in GenericHeap

[Hardvan]

• 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 69.56%. Comparing base (2083d68) to head (a028c35).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5980      +/-   ##
============================================
+ Coverage     69.55%   69.56%   +0.01%     
- Complexity     4696     4698       +2     
============================================
  Files           626      626              
  Lines         17154    17160       +6     
  Branches       3314     3314              
============================================
+ Hits          11931    11937       +6     
+ Misses         4766     4763       -3     
- Partials        457      460       +3     

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