base

Add capability APIs to VoiceInteractionService

The only API we currently need is one that tells us whether the system
is capable of running hotword detection for a given keyphrase+locale on
the hardware.

Also adds support in the KeyphraseEnrollmentInfo to provide an intent
for enrollment.

Change-Id: Iec102a4a94e7b161087b8d19785d761346e927c2