Allow Resizing on Parent Interface Selection Window

[_carl]

The window for selecting interface inheritance isn't resizable -- and is rather painful to use as a result since interface names from dependency libraries are almost always going to be long. Allowing this window to be resizable would be a simple way to make this more pleasant.

(Adding a search/filter option would also be great, along with just generally making all windows resizable, but that's a bigger ask, and has been requested elsewhere.) 

[crossrulz]

Related idea (NOT a duplicate of): All windows should be resizable!