Add ReverseStringUsingStack

[navaneedan07]

• 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 75.06%. Comparing base (24f4090) to head (ceb6b93).

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #6452      +/-   ##
============================================
+ Coverage     75.04%   75.06%   +0.02%     
- Complexity     5534     5539       +5     
============================================
  Files           685      685              
  Lines         19208    19219      +11     
  Branches       3706     3709       +3     
============================================
+ Hits          14414    14427      +13     
+ Misses         4239     4238       -1     
+ Partials        555      554       -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.

[DenizAltunkapan]

if you move this method in the existing class, please also add some tests for your method.

[navaneedan07]

All the requested changes have been made. Pls allow me to merge if my commit is perfect.
If any changes have to be made, pls post it.
I've been eagerly waiting to contribute

[DenizAltunkapan]

There should only be two Classes changed: ReverseString and its test-file instead of four Files, so that i can merge

[DenizAltunkapan]

Closes #6451