Conform to 1D VelocityTracker

The native VelocityTracker has been refactored to allow support of axes
beyond X and Y axes. To conform to this change, we are updating calls to
the native VelocityTracker. Furthermore, to support independent velocity
tracking for separate axes, we are updating the native/JNI methods
accordingly. With these changes, supporting new axes for velocity
tracking would only require changes at the native VelocityTracker level
only (besides creating a public API for our clients).

Bug: 32830165
Test: android.view.cts.VelocityTrackerTest unaffected; touch fling works

Change-Id: Ib0be0fc38c315ade2475cd53597a846e58016d14