Fix the Locale story in the hotword API

Tighten the API by taking in a locale rather than a string tag.
Tighten the checks when reading the enrollment metadata, bail out if any
attribute is missing or invalid.
Add missing recycle call for a TypedArray

Stop recognition when sound model(s) change. This is needed during
un-enrollment/re-enrollment.

Bug: 17187528
Bug: 17205230
Change-Id: Idb00b51ef8c4ea0a8f8993decea582223181fa3d