[Dual Shade] Match the HUN draw bounds to notifications stack alignment.

Previously, HUN draw bounds would take up the entire screen width, even
when notifications could only be rendered on half of the screen width.
This caused unintended consequences with touch handling.

Fix: 441599011
Bug: 440416099
Test: Manually tested with NSSL debug lines by receiving a HUN in both
 narrow and wide form factors, on both Dual and Split shade modes.
Flag: com.android.systemui.scene_container
Change-Id: Ie5638c6e6f9614bbb2534970f21a82e76904873c