Introduce a shared class for test utilities. am: 3d0d9ab345 am: 386ae9b0ec am: 93ce9c5ddb

Original change: https://android-review.googlesource.com/c/platform/art/+/2210256

Change-Id: Ic093de8763b5819053ffc8270427c52b39bce224
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>