refactor: DecimalToHexadecimal

[alxkm]

Rename the previous file.
Improving the code to make it more readable.
Adding additional tests to this algorithm.

• 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 84.61538% with 2 lines in your changes missing coverage. Please review.

Project coverage is 43.04%. Comparing base (d80fd0c) to head (ced0f5b).

Files	Patch %	Lines
...healgorithms/conversions/DecimalToHexadecimal.java	84.61%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5337      +/-   ##
============================================
+ Coverage     43.03%   43.04%   +0.01%     
- Complexity     2666     2670       +4     
============================================
  Files           522      522              
  Lines         15474    15472       -2     
  Branches       2950     2952       +2     
============================================
+ Hits           6659     6660       +1     
+ Misses         8532     8527       -5     
- Partials        283      285       +2     

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