Add method to wait for property to have given value. am: ac3d3e2d4f am: 7d62f81fb9

Original change: https://android-review.googlesource.com/c/platform/system/librustutils/+/2584504

Change-Id: I5c09e43bb924d3a5cd5d915c64680801b5992f68
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>