[Flexiglass] Turn off SCOLL_FLING CUJ tracking from the NSSL

Disable tracking CUJ_NOTIFICATION_SHADE_SCROLL_FLING events from the
NSSL and NSSLC, because moving the stack updown by scrolling,
overscrolling or flinging is now controlled through the Placeholders.

This CL also flags off some bigger junks of the remaining scroll logic.

Bug: 360100111
Test: verify that the new assertions are not hit with flexi on
Flag: com.android.systemui.scene_container
Change-Id: I88a7aab43980c5c42138ea0b7e4523fb15648bdc