test: move test/variants into test/data

[aucampia]

Summary of changes

This is to bring it in line with other test data.

Checklist

• Checked that there aren't other open pull requests for
  the same change.
• Checked that all tests and type checking passes.
• Considered granting push permissions to the PR branch,
  so maintainers can fix minor issues and keep your PR up to date.

[ghost]

yep.