Rename HotwordAudioStreamManager and add Javadoc am: 714691fc46

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20618388

Change-Id: I6ee17b3ef97947efc674eeca38bb69550c2fa64a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>