RecognitionEvent.getHalEventTimestampMillis API

RecognitionEvent API for exposing the timestamp
which represents the time the SoundTrigger HAL emitted a
RecognitionEvent

Test: atest CtsVoiceInteractionHostTestCases
Test: atest SoundTriggerTest
Bug: 265852186
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:1d92efdd4af397d547b595ac9cd395c4df1e0156)
Merged-In: I9f2dff736cf29661046a7995b58dd03a106efb16
Change-Id: I9f2dff736cf29661046a7995b58dd03a106efb16