Reattaching and dismissing notifications when detached.

This change re-applies the previous behavior that had to be reverted.
Essentially:
* Magnetically detaching a notification makes it dismiss if released
  from touch.
* Notifications re-attach to the edge of the screen when dragged past a
  re-attachment threshold.

Test: MagneticNotificationRowManagerImplTest
Test: NotificationSwipeHelperTest
Flag: com.android.systemui.magnetic_notification_swipes
Bug: 397418247
Bug: 397418669
Change-Id: I9ad253d9e39160baf8a55df19abe38d298d3f33a