Pass shared node state changes on to every layer

When several views import the same scene, their layers walk the same
render nodes. updateGlobalNodeState() clears a node's ActiveDirty and
TagDirty flags and reports the change only to the layer that ran it
first. The other layers saw a clean node, skipped the restat, and kept
their stale filtered node lists until something else dirtied the tree.
A model that became visible, or changed layers, therefore stayed hidden
or visible in some of the views.
Issue is now solved by creating a global state tracking variable giving
the other layers a chance to catch the change.

Pick-to: 6.12 6.12.0
Fixes: QTBUG-150709
Change-Id: If8606c6592d8b3304b2b52e4d73ab8471a7b1dc9
Reviewed-by: Tomi Korpipää <tomi.korpipaa@qt.io>
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>