Include global functions in unscoped_variables lint

[Kampfkarren]

If they're not already. If they are, add it to the test file.

[Corecii]

We ran into a case recently where this lint would have helped massively. A function accidentally defined globally almost delayed a release for at least a day!

Luckily, when I joined to help I had an extension that highlights globals and locals differently, so it stood out to me. This is something that other team members expected Selene to catch since they'd grown use to it catching so many other global vs local issues.