refactor: MergeSortNoExtraSpace

[alxkm]

Refactor MergeSortNoExtraSpace

Changing naming

Adding test

• 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 40.30%. Comparing base (1426460) to head (c80a67e).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5277      +/-   ##
============================================
+ Coverage     40.06%   40.30%   +0.24%     
- Complexity     2467     2480      +13     
============================================
  Files           519      519              
  Lines         15481    15473       -8     
  Branches       2952     2950       -2     
============================================
+ Hits           6202     6236      +34     
+ Misses         8988     8945      -43     
- Partials        291      292       +1     

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