[Flexiglass] Don't recalculate expandFraction in the NSSL

Don't override the expandFraction received from
NotificationScrollViewModel.
Fork NSSL.setExpandedHeight, and remove all the parts that are
non-functional in Flexiglass.

Bug: 332574413
Fixes: 332577544
Test: check notifications during shade/expand collapse in
different states:
 - single/split shade
 - launcher/lockscreen
 - no notifications/scrollable notifications
 - hun displayed/not displayed

Flag: com.android.systemui.scene_container

Change-Id: Idb04c4b93df3081336d5a00b7a67f88123dafbf8