Define the AIDL interface for AuthGraph key exchange. am: 0e2495f107 am: 5c44262ee7

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2606133

Change-Id: I0595109be548b5f50a2a7a73757e2dfac69f5cba
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>