Add optional timeout to PropertyWatcher::wait. am: 9349cf0598 am: 6bf2d6abc3 am: 7168a32209

Original change: https://android-review.googlesource.com/c/platform/system/librustutils/+/2584503

Change-Id: I0c0b0460fc93f9ae9d560b1a1edb46c696482aa0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>