Install krunner desktop file to ${KDE_INSTALL_APPDIR}

Summary:
To avoid kwin warnings in ~/.local/share/sddm/wayland-session.log such as :
kwin_core: Could not find the desktop file for "/home/meven/kde/usr/bin/krunner"
kwin_core: Did not grant the interface "org_kde_plasma_window_management" to "/home/meven/kde/usr/bin/krunner" . Please request it under X-KDE-Wayland-Interfaces

Reviewers: apol, #plasma

Reviewed By: apol

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D24857