Introduce a shared class for test utilities. am: 3d0d9ab345 am: 386ae9b0ec am: 93ce9c5ddb am: 884423ac1a am: 238b868963

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

Change-Id: I99d406f16dea6f4883596f42abedb6858690503e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>