Add some way to check if the open popup was opened from within a `Ui`

[lucasmerlin]

Is your feature request related to a problem? Please describe.
This would be really useful in Uis that are shown based on some condition, e.g. in the rerun list item we only show some buttons on hover. The button should stay visible if a menu is open, and currently you'd have to a check for every menu if it's open and override the show_on_hover behaviour.

Describe the solution you'd like
This could be solved by storing the UiStack when opening a popup, then we could check if the current ui is in the popups stack.