[flexiglass] Show notification icons on AOD

The AodNotificationIcons composable existed already, but it was unused
after the refactor from I40d0dc8d8dd4d25976127ed5b7a2ee0205e11976.

Also removed the unused flows from isNotifIconContainerVisible.

Fix: 437344034
Test: manual - with and without an AOD RON, folded and unfolded, pulsing
Flag: com.android.systemui.scene_container
Change-Id: I36a93ea92ee933ce3fc27a76230787659c970d96