Allow shallow-angle flings in AssistantTouchConsumer

While any angle above 22 degrees from horizontal is permitted for
drag invocations, the SwipeDetector used to detect flings only
allowed angles within 45 degrees of vertical. This changes to using
GestureListener and permits flings in the 22-45 degree region (as
well as up to vertical).

Test: manual
Bug: 135011207
Change-Id: I8e08650395917341869b27ff381f32268fadcb3c