Fix digital wellbeing toast being initialized multiple times

Digital Wellbeing toast state was being updated several times together with the app icon unnecessarily. This was causing a recreation of the Digital Wellbeing and replacing the banner attached to the TaskView multiple times, leading to heavy UI thread work and jumpy animations in some cases.

Bug: 271428408
Test: manual
Change-Id: I1a2a1423924efb0fb3c1e66826e3ab11211dcfb7