Migrate SoundTrigger implementation to new service

The API offered by SoundTrigger.java is now implemented on top of
the new soundtrigger_middleware service.
There is no longer any need for JNI - the API now talks directly
with the AIDL interface of the new service.

In the process, some annotations and input validation have been added
to improve the overall quality of this API.

Change-Id: I731ffd5a275b88f38d84dd3daa022a13f97a5ee1
Bug: 142070343