[Dual Shade] Hide the status bar when either shade is open.

Both notifications shade and quick settings shade render a
status-bar-like header, which we don't want to conflict with the status
bar.

Fix: 394149273
Test: Added unit tests.
Test: Manually by expanding and collapsing the shades over Lockscreen
 and Gone scenes and verifying only the shade header is rendered.
Flag: com.android.systemui.scene_container
Change-Id: I716ad910b94644f238c3ba06cd6cce6baaf15b10