Introduce soundtrigger HAL v3

This is the initial AIDL version of the soundtrigger HAL.
It is functionally equivalent to v2.4 (HIDL), but with a clean-up
interface that removes obsolete / legacy functionality and conforms to
AIDL style.

Test: Mocked the HAL and observed framework logs for basic use-cases.
Change-Id: I4525301ad1205cf41937a98b7b9f67f052cb5bd9