AppEvents was always a service object in disguise, so we should move it
to the correct place in the application. Doing this allows other service
objects to inject it easily without container access.
In the future we should also deprecate `this.appEvents` without an
explicit injection too.
We refactored some code to avoid app event leak in tests at c462c2f2
Unfortunately this broke all background notifications in title and they
were broken for the past multiple months.
