Input events go to the tooltip because it's added to `popup_list` in
DisplayServer `popup_open`. I think there's no harm in tooltips being omitted
from the list, so this commit blocks non-popup windows from being added if they
have `FLAG_NO_FOCUS` and `FLAG_MOUSE_PASSTHROUGH`.
I'm not happy with this way of detecting tooltips. It'll also catch other
windows where this behavior may or may not be wanted.
I thought about adding `FLAG_TOOLTIP`, but went with the smaller change for
now.
Fixes#79500.
ae1e2182ec