Implement multi-finger multi-tap gesture matchers for accessibility

This matcher would detect following gestures when accessibility flag
flagRequestMultiFingerGestures enabled:

- 2-finger single tap
- 2-finger double tap
- 2-finger triple tap
- 3-finger single tap
- 3-finger double tap
- 3-finger triple tap

Bug: 142277684
Bug: 142276516
Bug: 136131815
Test: atest AccessibilityGestureDetectorTest TouchExplorerTest GestureManifoldTest

Change-Id: I0aa6e858520d0b36c81df6fe08fd86d7d0803d5a