example AIDL HAL extension

This CL shows an example of how to use and retrieve a HAL extension.

Bug: 136027762
Test: run HAL and:
- use "dumpsys --pid android.hardware.vibrator.IVibrator/default" to
make sure that the HAL I'm running is the binary being added.
- VtsHalVibratorTargetTest
- test-vintf-vibrator-ext-client

Change-Id: I8614007a727e8e05ba4667c2cd1623ce936a1609