Improvements to Vampire Number

[Shisoik]

Several improvements to maths/VampireNumber code:

1. Fixes a bug in same length of fangs detection for pseudo vampire numbers. Now it is done in the most straight-forward way.
2. Adds tests for the VampireNumber class.
3. Fixed several typos in code and comments.
4. Generally simplifies code and improves readability.

• 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 81.81818% with 2 lines in your changes missing coverage. Please review.

Project coverage is 73.78%. Comparing base (2da56d6) to head (e25809d).

Files with missing lines	Patch %	Lines
...in/java/com/thealgorithms/maths/VampireNumber.java	81.81%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6110      +/-   ##
============================================
+ Coverage     73.65%   73.78%   +0.13%     
- Complexity     5114     5119       +5     
============================================
  Files           658      658              
  Lines         17649    17632      -17     
  Branches       3396     3391       -5     
============================================
+ Hits          12999    13010      +11     
+ Misses         4147     4118      -29     
- Partials        503      504       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Shisoik]

IMHO, limiting tests to just 3 static imports and forbidding to static import org.junit.jupiter.api.Assertions.* is too strict and actually hurts readability. Not gonna argue, just a thought.

[siriak]

Looks good, thanks!