feat: FlashSort implementation

[alxkm]

FlashSort implementation.
Adding standard test.

This PR implements this feature request #5304

• 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

Attention: Patch coverage is 97.22222% with 2 lines in your changes missing coverage. Please review.

Project coverage is 42.04%. Comparing base (324a35a) to head (13ec839).

Files	Patch %	Lines
...c/main/java/com/thealgorithms/sorts/FlashSort.java	97.22%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5305      +/-   ##
============================================
+ Coverage     41.78%   42.04%   +0.26%     
- Complexity     2586     2614      +28     
============================================
  Files           521      522       +1     
  Lines         15493    15565      +72     
  Branches       2958     2969      +11     
============================================
+ Hits           6473     6544      +71     
- Misses         8723     8724       +1     
  Partials        297      297              

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[siriak]

Looks good, thanks!