Add factorial recursion

[konduri-lakshmi-prasanna]

• 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

❌ Patch coverage is 74.28571% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.83%. Comparing base (b312567) to head (d616361).

Files with missing lines	Patch %	Lines
...in/java/com/thealgorithms/recursion/Factorial.java	0.00%	7 Missing ⚠️
...java/com/thealgorithms/strings/StringRotation.java	75.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6794      +/-   ##
============================================
- Coverage     77.84%   77.83%   -0.02%     
- Complexity     6394     6405      +11     
============================================
  Files           733      736       +3     
  Lines         21333    21368      +35     
  Branches       4183     4188       +5     
============================================
+ Hits          16607    16632      +25     
- Misses         4058     4067       +9     
- Partials        668      669       +1     

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

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[vil02]

Please notice the duplicate FactorialRecursion.java.

Also please open one PR for one algorithm (and tests of it) - it is easier to review.

[konduri-lakshmi-prasanna]

Added a recursive implementation of the factorial algorithm under com.thealgorithms.recursion.
Includes proper input validation for negative numbers
Added comprehensive JUnit test cases
Conforms to repository checkstyle (private constructor for utility class)