Migrate `ReverseStringRecursive` functionality and tests to `ReverseString`

[DenizAltunkapan]

What would you like to share?

Delete the existing file ReverseStringRecursive.java and move its functionality and test methods from ReverseStringRecursiveTest.java to ReverseString.java and ReverseStringTest.java, respectively.

• Delete ReverseStringRecursive.java
• Delete ReverseStringRecursiveTest.java
• Move the recursive string method from ReverseStringRecursive to ReverseString
• Move the test methods from ReverseStringRecursiveTest to ReverseStringTest
• Ensure the added methods in ReverseStringTest are correctly formatted according to project standards

Expected Outcome

• ReverseStringRecursive.java and ReverseStringRecursiveTest.java are deleted
• Recursive method is part of ReverseString

[DenizAltunkapan]

Closed in #6504