Fix NSSL migration and falsing

Touch events were getting processed multiple times by the
FalsingManager, leading to incorrect falsing and the UI being
reset. These fixes ensure each touch gets processed once, and by the
correct owner.

Fixes: 314302258
Test: manual; observe falsing logs when swiping on shade
Flag: ACONFIG com.android.systemui.keyguard_shade_migration_nssl
DEVELOPMENT

Change-Id: I228090b917a25a7d1ac459c10f0a1d98167d435a