Make checkboxes/radiobuttons use Window Background in windows and View Backround in lists

Summary: If the widget has an item view parent, use the View Background color. Otherwise, use Window Background.

Test Plan: {F7881597, size=full}

Reviewers: #vdg, #breeze, hpereiradacosta, ngraham

Reviewed By: #vdg, hpereiradacosta

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26639