Cleanup icon handling
Summary:
- Remove unnecessary KIconLoader search paths
- Prefer QStyle over KIconLoader for determining sizes
- Prefer icons over pixmaps on QActions
Reviewers: mlaurent
Reviewed By: mlaurent
Subscribers: kde-pim
Tags: KDE PIM
Maniphest Tasks: T11637
Differential Revision: https://phabricator.kde.org/D24801