[IconApplet] Port KRun to ApplicationLauncherJob
Test Plan:
Open the Application Launcher, right click any app -> Add to Panel (Widget),
then click the icon on the panel, it should launch.
Reviewers: Plasma, broulik, dfaure
Reviewed By: dfaure
Subscribers: dfaure, ngraham, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D29687