Allow quick switch from 3P launcher home in 2 button mode

Only the FallbackSwipeHandler supports quickswitch mode on the
home screen, but we only used that handler for fully gestural
mode. Now we also use that handler for 2-button mode if both
of these conditions are met:
- User is on the home screen
- User swipes right on the nav region (instead of up)

Also fix issues with continuous quick switch gestures by setting
the appropriate end target NEW_TASK instead of HOME.

Bug: 140467002
Change-Id: I8f327638b48cf4c0acb1ebe265b7846afac6759b