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 74.64%. Comparing base (dba2d86) to head (5497bb5).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #6366   +/-   ##
=========================================
  Coverage     74.64%   74.64%           
- Complexity     5448     5449    +1     
=========================================
  Files           682      682           
  Lines         19012    19011    -1     
  Branches       3672     3672           
=========================================
  Hits          14191    14191           
  Misses         4262     4262           
+ Partials        559      558    -1     

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