Only pilfer once in InputSession.

This change modifies the behavior of InputSession to only pilfer
motion events once.

Fixes: 333596426
Test: atest InputSessionTest#testPilferOnce
Flag: ACONFIG com.android.systemui.dream_input_session_pilfer_once DISABLED
Change-Id: Ied60cbabcb4bed53f9ec77e580d722338f4de448
3 files changed