Move x Folder Into Tests Directory and Clean Up Test Structure

[Biswajitn23]

Description

• Moved the experimental/placeholder x folder from the project root into the tests directory to maintain a clean and organized structure.
• All files from x are now under tests/x, including subfolders and database files.
• The test directory is now organized by module, with subfolders for individual functions/class methods as per best practices.
• Removed the old x folder from the project root.

This change improves maintainability and scalability of the test suite.