Support back-to-back soundtrigger recognitions

This change allows the HAL driver, at its discretion, indicate that
recognition is still active after a success event.
This is achieved by an additional flag added to the event.
The behavior to support this case has already been in place, for the
sake of supporting a FORCED event. This change just generalizes this
behavior to be able to cover SUCCESS as well.
For b/w compat, when the status is FORCED, we override the new flag
with 'true', indicating that recognition is still active.
We do not allow the flag to be set for status codes other than FORCED
or SUCCESS.

Test: atest FrameworksServicesTests:{SoundTriggerMiddlewareImplTest,SoundHw2CompatTest}
Test: Manual verification of sound trigger operation by invoking the
      assistant and now playing multiple times.
Bug: 186031938
Change-Id: Ie4edf82607c72ccb0b8d90a828b04c93153ec8f3