Add SoundTriggerManager to handle calls to SoundTrigger

- We are abstracting out the nitty-gritty details of the code that talks
  to the SoundTrigger APIs as the
  VoiceInteractionService is mostly interested in the "voice" related
  aspects of the sound trigger APIs

Change-Id: I4a450033040280f2e67d06785d2b05a0e5cdc192