Add KthSmallestElementInBST implementation with test

[shreyash24-tech]

• 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 algorithms include a corresponding test class that validates their functionality.
• 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 79.34%. Comparing base (0c79d33) to head (f8cd208).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #7267      +/-   ##
============================================
+ Coverage     79.31%   79.34%   +0.02%     
- Complexity     6990     6997       +7     
============================================
  Files           781      782       +1     
  Lines         22958    22972      +14     
  Branches       4510     4513       +3     
============================================
+ Hits          18210    18226      +16     
  Misses         4020     4020              
+ Partials        728      726       -2     

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[github-actions]

This pull request has been automatically closed because its workflows or checks failed and it has been inactive for more than 14 days. Please fix the workflows and reopen if you'd like to continue. Merging from main/master alone does not count as activity.