refactor: IntrospectiveSort

[alxkm]

Improving code readability, simplify in some places
Adding general sorting test as it provides better coverage
Adding Java docs with description of methods

• 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 58.06452% with 13 lines in your changes missing coverage. Please review.

Project coverage is 42.29%. Comparing base (66bfaff) to head (a5be829).

Files	Patch %	Lines
...ava/com/thealgorithms/sorts/IntrospectiveSort.java	58.06%	12 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5316      +/-   ##
============================================
+ Coverage     42.18%   42.29%   +0.10%     
- Complexity     2621     2627       +6     
============================================
  Files           522      522              
  Lines         15537    15540       +3     
  Branches       2964     2965       +1     
============================================
+ Hits           6555     6572      +17     
+ Misses         8685     8671      -14     
  Partials        297      297              

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