ahat: support java.lang.ref.Finalizer

Because some implementations use that in contrast to ART's
java.lang.ref.FinalizerReference to track finalizers.

Bug: 111867529
Test: m ahat-test, with new test added.
Change-Id: Id9ae4e32f0e6c852fabbb73c790dbd7d9f28c51f
4 files changed