port to PlasmaComponents3
Summary:
the pieces of old components we couldn't control, like the combobox menu
didn't react to palette change
BUG:397845
Test Plan: applet still works and looks identical, combo popup changes color dinamically
Reviewers: Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D15165