Validation pytest fix

[quinnylee]

Resolves non-determinism in the validation test suite. Closes #72

Changes

• replaced os.system calls with pathlib, shutil, and requests methods
• replaced subprocess.run calls with response and tarfile methods

Testing

1. ran the tests on macOS/arm64, Ubuntu/x86

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Visually tested in supported browsers and devices (see checklist below 👇)
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

Testing checklist

Target Environment support

• Linux