[flexiglass] Reset NSSL stack bounds from the unoccluded GONE scene

NSSL can display some content on the GONE scene (HUNs), and therefore
we'd like to have some consistent values for the stack bounds to be set.
However we only want these values if the GONE scene is NOT occluded by
the shade.

Fixes: 383321837
Test: open dual shade over gone -> notifications are positioned correctly
Flag: com.android.systemui.scene_container
Change-Id: I37a7e9880c47d20d051900df95d76fcfb4d12690