KF5 port: remove deprecated KStringHandler and KTabWidget usage
Summary:
KStringHandler::naturalCompare() was replaced with QCollator (according to deprecating comment, other commits did it the same way)
KTabWidget was replaced with QTabWidget - there were no special KTabWidget functions at all.
Test Plan: TriggerConfig works as before
Reviewers: KDE Games, ltoscano
Reviewed By: ltoscano
Subscribers: ltoscano, KDE Games
Differential Revision: https://phabricator.kde.org/D7417