LeAudio: Add empty audio provider implementation am: ccceb2f3 am: 9b2313d1 am: 1b881b9b

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



Change-Id: Ibbe1837c7fc0de5891da936dd5925d8bf9167691
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>