Allow global import in class without namespace

[chr-hertel]

Aims to fix #4726

[chr-hertel]

This is not sufficient and tests are failing. Will have another look in sunday.

[SpacePossum]

Thanks for making the PR and putting time and effort into looking into this issue.
The solution direction picked here seems a bit late in the stack I feel, I think the underlying issue is within the logic that should correctly figure out which imports are done within the scope of the namespace that is relevant. I'm trying to fix this in another PR (#6197) which still needs a bunch of work, but wanted to let you know that we might be looking and working on the same thing here :)

[SpacePossum]

fixed in #6197 (I hope)