Replace deprecated getRunningTasks with another solution

[TristanWiley]

In IncomingEventService, getRunningTasks is deprecated. This is used to get the foregroundTaskInfo and determine if our app is in the foreground.

We need a non-deprecated way to do this.

[TimCastelijns]

As an alternative to using ActivityManager, it's possible to have the application class listen for activity lifecycle changes. Then you can derive that the app is in the background if Application.currentForegroundActivity = null or something. Not implying it's better, but now you have 2 options 🙂