Add suport for KF6 notifications
KF6 applications now store their notifications config in the
knotifications6/
path instead of knotifications5/
.
Scan the new path first on the KCM and the library, but still support the old path for compatibility with KF5 apps.
TEST: There are few KF6-only applications that doesn't show up in the KCM without this MR, but here is one, the timer applet from plasma-addons ("Timer"). All the KF5-only apps are still shown correctly
Edited by Ismael Asensio