Use the LockscreenStackBounds during transition LS -> Shade

Keep using the lockscreen stack bounds when transitioning from the
lockscreen scene to shade for visual consistency. Otherwise, the stack
will jumps to its location in Shade, and overlaps with the smart space
before the animation actually starts.

Fix: 436817577
Test: manual
Flag: com.android.systemui.scene_container
Change-Id: I7d2e8d5ecbae3985306a4d515bbf6d9fea2b8c75