[Dual Shade] Fade out lock screen notifications when QS shade is open.

Fix: 433538684
Test: Manually by opening and closing QS shade on lock screen on a wide
 screen device, and observing the notifications fade out/in respectively
Test: Unit tests still pass.
Flag: com.android.systemui.scene_container
Change-Id: I837ebf93da99ebae513b961c3c6f9c53de3a6dea