Allow children of PopupDialogs to process input events first

[trimbe]

Fixes #7635

Description of the problem being solved:

Input events are handled by PopupDialog before being passed to its child controls, allowing an input to be handled twice. Now allows child controls to handle/consume events first.  

Steps taken to verify a working solution:

• Using a build with at least 7 sockets, open the item trader dialog and scroll while hovering a dropdown. The dropdown should scroll without the item slot view scrolling.

Link to a build that showcases this PR:

https://pobb.in/ZCKPLQT3VO6d