LeAudio: Add empty audio provider implementation am: ccceb2f3 am: 9b2313d1

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2824794



Change-Id: I894e0b47c39283d3958695f487740cce003b56d5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>