refactor: refactor Ceil and improved tests

[alxkm]

Ceil Class Refactor:

• Simplified the Ceil.ceil(double) method for better clarity and correctness.
• Replaced (int) casting with (long) to handle edge cases and large numbers more safely.
• Updated method-level JavaDoc and added class-level documentation for better understanding and maintainability.

Test Refactor:

• Migrated CeilTest to use JUnit 5 @ParameterizedTest with @CsvSource.
• Enhanced test readability, scalability, and coverage.
• Ensures better structure and allows easier future additions of test cases.

• 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

All modified and coverable lines are covered by tests ✅

Project coverage is 74.63%. Comparing base (f325279) to head (2b6f328).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6366      +/-   ##
============================================
- Coverage     74.63%   74.63%   -0.01%     
  Complexity     5452     5452              
============================================
  Files           682      682              
  Lines         19017    19016       -1     
  Branches       3674     3674              
============================================
- Hits          14193    14192       -1     
  Misses         4265     4265              
  Partials        559      559              

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