One-finger swipe: remove unnecessary allocations.

Part of the old swipe code, which was copied over to the new swipe detector, used GesturePoint objects because it needed to track the time of each entry in the gesture path. This is no longer necessary because we use handlers to cancel the gesture on a delay. This change makes the whole class use PointF which avoids allocating a new PointF for some subset of the GesturePoints during the gesture recognition process.

Bug: 136131815
Test: atest GestureManifoldTest AccessibilityGestureDetectorTest TouchExplorerTest
Change-Id: I1c89122d7f27b52a25e777667e34fec246d5c21f