[Status Bar] Display notif icon area during HUN even in lights out mode.

Fixes: 291173113
Test: manual: Trigger HUN while in fullscreen app -> verify notif icon
for HUN displays
Test: manual: Same verification after changing font or display size
(since PhoneStatusBarTransitions & other classes get re-created on
display change)
Test: atest PhoneStatusBarTransitionsTest
HeadsUpAppearanceControllerTest

Change-Id: I7b16486b2b6211c03f5f309649af89fe2d311b04