feat(C++): add deleteFolderRecursive sample

[nidhiii-27]

This adds a sample demonstrating how to recursively delete a folder in a hierarchical namespace bucket.

Fixes: b/521168740

[gemini-code-assist]

Code Review

This pull request adds a new sample function DeleteFolderRecursive to demonstrate recursive folder deletion, registers it in the command-line interface, and adds a test case in AutoRun. The reviewer suggested enhancing the test case by creating a nested subfolder structure to properly demonstrate and verify the recursive deletion behavior of the API.

[gemini-code-assist]

To properly test and demonstrate the recursive deletion behavior of DeleteFolderRecursive, it is recommended to create a nested subfolder structure inside the target folder. Otherwise, the test only deletes an empty folder, which does not fully exercise the recursive aspect of the API.

  CreateFolder(client, {bucket_name, folder_id});
  CreateFolder(client, {bucket_name, folder_id + "/subfolder"});
  DeleteFolderRecursive(client, {bucket_name, folder_id});

[nidhiii-27]

Done

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.19%. Comparing base (fd73bee) to head (433d4e2).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16153      +/-   ##
==========================================
- Coverage   92.20%   92.19%   -0.01%     
==========================================
  Files        2264     2264              
  Lines      208864   208864              
==========================================
- Hits       192579   192567      -12     
- Misses      16285    16297      +12     

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