authgraph: add placeholder VTS test am: c8625a8963 am: ad80c36b3c am: 2fa2bbb88c

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2750487

Change-Id: Ibcbd888d01154dae2ed9a2c04d65c25385940d49
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>