Merge "DownmixProcess: Add tests to validate the downmix process." into main am: ab269e2f am: 157e9549 am: aed26301

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2849236



Change-Id: I078925d0ea8f67123e5f638334c3b2a2637db3ba
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>