refactor: cleanup PancakeSort

[alxkm]

Cleanup PancakeSort, to improve code readability.

Change previous test to standard sorting test, as it provide better coverage.

• 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 41.11%. Comparing base (97d416e) to head (c2069a3).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5295      +/-   ##
============================================
+ Coverage     41.01%   41.11%   +0.10%     
- Complexity     2526     2528       +2     
============================================
  Files           519      519              
  Lines         15444    15413      -31     
  Branches       2947     2947              
============================================
+ Hits           6334     6337       +3     
+ Misses         8816     8782      -34     
  Partials        294      294              

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