audio: Disable the C++ backend for android.hardware.audio.core

android.hardware.audio.core will need to use FMQ,
which does not support the C++ backend in the AIDL version.

Migrate VTS tests from the C++ backend to the NDK backend.

Bug: 205884982
Test: atest VtsHalAudioCoreTargetTest
Merged-In: Ia5d29126afdb4bb97dd063a032b96ab83b9ce36e
Change-Id: Ia5d29126afdb4bb97dd063a032b96ab83b9ce36e
(cherry picked from commit 8fcc4424)