Add classification to MotionEvent

Classification will help categorize the current touch
stream. For example, a DEEP_PRESS classification could be generated
if the system has
determined that the user is trying to press harder on the screen.

This classification could be generated by an ML model.

Test: integration tested by observing the classification being generated
by the InputClassifier HAL.
Bug: 62940136

Change-Id: If72d69a41ff25c8a7f351bac0d86db6fd73500a1