Install bluetooth audio VINTF fragment in apex

Previously, android.hardware.bluetooth.audio-impl was installed with no
use and the attached vintf was fulfilled by the
com.android.hardware.audio apex.

For cleanup, we no longer install android.hardware.bluetooth.audio-impl
separately (for cuttlefish) and install the VINTF inside the apex.

Bug: 312265159
Test: atest VtsHalBluetoothAudioTargetTest
Change-Id: I31e0ccd6a8c3c00565159f2be7fe3bf4d70e9ddf