[Folder View] Use an inactive highlight effect when something else has focus
Summary:
The theme SVG doesn't have a concept of "inactive selection highlight", so we need to
manufacture our own by reducing the opacity of the selection highlight.
Thanks to @broulik for suggesting the necessary code changes in the bug report.
FEATURE: 375501
FIXED-IN: 5.18.0
Test Plan:
Reviewers: Plasma, VDG, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: broulik, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D25160