Refactor: Move ./test_data/ to dedicated ./tests/test_data/ directory

[jaegeral]

This pull request moves the test data from ./test_data to ./tests/test_data. This change streamlines the project's folder structure by consolidating test-related files within the tests directory. This improves organization and makes it clearer where test resources reside.

Specifically:

• Moved the ./test_data directory and its contents to ./tests/test_data.
• Updated any references to the old test data path within the codebase to reflect the new location. (If applicable, list specific files or modules that were updated. E.g., "Updated references in tests/test_importer.py and tests/test_analyzer.py.")

This change aims to improve the overall project structure and maintainability. It does not introduce any new functionality or change existing behavior.

Checks

• All tests succeed.
• Unit tests added.
• e2e tests added.
• Documentation updated.

Closing issues

Related to: #3184

[jkppr]

lgmt