[Flexiglass] Allow to increase Notif height with drag-to-expand on the LS

As the user drags down on a Notification on the LS, the Notification
will gradually increase its actual height. However StackSizeCalculator
will override it with a restricted height for the Lockscreen. Previously
we were making an exception for this restriction based on
"fractionToShade", but since NSSL cannot control the Shade expansion state
directly anymore, we cannot rely on this value.

This CL exempts Notifications from the LS constraints in StackSizeCalculator
while the user is dragging on them.

Bug: 359957196
Test: Drag down on a Notification on the LS -> Check if its rendered height is growing
Flag: com.android.systemui.scene_container
Change-Id: I1f223159d1701f7e931ace38069df03f04365a09