Split onPointerDown to onPointerDown and onUiReady

Previous behavior:
1. Detect a valid touch.
2. Enable HBM.
3. Notify the HAL about onPointerDown when HBM is enabled.

New behavior:
1. Detect a valid touch and report onPointerDown right away.
2. Enable HBM.
3. Notify the HAL about onUiReady when HBM is enabled.

Bug: 184361899
Test: atest UdfpsControllerTest
Test: on device
Change-Id: I48aa3945902a8ca151aabe61a5e71e910773bd88