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

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

Change-Id: I5f4c2a1bd1a021d77e891285587b50308d35021f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>