Add audio stream and usage for virtual assistant

New stream type: AUDIO_STREAM_ASSISTANT
This is intended to be used by a virtual assistant like
Google Assistant, Bixby, etc.

The audio stream has own volume alias and the volume
does not change by volume changes of other streams.

Bug: 123745215
Test: make
Change-Id: I3696d8fba32070954cc6a330574af8507fea7a74
diff --git a/current.txt b/current.txt
index 1fe17d5..b54c16a 100644
--- a/current.txt
+++ b/current.txt
@@ -605,7 +605,7 @@
 2df5d5866b37776f25079c0e54b54350a2abe4e025a59c9e02a7d3abe8ca00e8 android.hardware.audio@6.0::IStreamIn
 78e4138cc8307c11fc777c3bd376e581ba4ba48196b05ca1d7cdfa515c87b48a android.hardware.audio@6.0::IStreamOut
 997fdaad7a9d17ee7e01feb7031a753e2365e72ad30b11d950e9183fabdf3844 android.hardware.audio@6.0::IStreamOutCallback
-1349686814402fa10f711cc5763bc629aafc64a5f5843b4b21b8cd86ffb923e6 android.hardware.audio.common@6.0::types
+8c4232772efeb9905b4c287723e0ee8b2c4bf5ba11728d051171b070e3d79144 android.hardware.audio.common@6.0::types
 817930d58412d662cb45e641c50cb62c727e4a3e3ffe7029a53cad9677b97d58 android.hardware.audio.effect@6.0::types
 525bec6b44f1103869c269a128d51b8dccd73af5340ba863c8886c68357c7faf android.hardware.audio.effect@6.0::IAcousticEchoCancelerEffect
 8d76bbe3719d051a8e9a1dcf9244f37f5b0a491feb249fa48391edf7cb4f3131 android.hardware.audio.effect@6.0::IAutomaticGainControlEffect