Improve touch event resampling.

Fixed a few bugs related to the id-to-index mapping for
pointer coordinates.

Tightened the bounds on the resampling time interval to
avoid predicting too far into the future.

Only lerp X and Y components of motion events.

Alter the future to satisfy past predictions.  (Rewrite touch
events to conceal obvious discontinuities.)

Added a system property to control whether resampling is enabled
for debugging purposes.

Bug: 6375101
Change-Id: I35972d63278bc4e78148053a4125ad9abeebfedb