Add tests, remove main in PalindromePrime

[Hardvan]

• 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 94.73684% with 1 line in your changes missing coverage. Please review.

Project coverage is 64.30%. Comparing base (596c614) to head (5265736).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...n/java/com/thealgorithms/misc/PalindromePrime.java	94.73%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #5773      +/-   ##
============================================
+ Coverage     64.05%   64.30%   +0.24%     
- Complexity     4177     4216      +39     
============================================
  Files           584      587       +3     
  Lines         16332    16390      +58     
  Branches       3152     3167      +15     
============================================
+ Hits          10461    10539      +78     
+ Misses         5445     5421      -24     
- Partials        426      430       +4     

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[siriak]

Looks good, thanks!