[Flexiglass] Set Stack bounds directly on the NSSL

When the NSSL's content is changing, it invalidates the
NotificationPlaceHolder's measurements. The placeholder then measures,
and reads the current stack height from the NSSL directly. Once the
placeholder is laid out, it sends back the calculated stack bounds
via the recommended arch layers (viewmodel-interactor-repository) to
the NSSL.

This CL sets the calculated stack bounds from the placeholder to the
NSSL directly, and removes doing it through the viewmodel.

Bug: 330667757
Test: Check the NSSL scrolling behaviour.
Flag: ACONFIG com.android.systemui.scene_container DEVELOPMENT
Change-Id: Idb335a11520cdb0914b005faaa7deff3637177a7