Implement Reference.refersTo for layoutlib

The ART version of java.lang.ref.Reference implemented the method
refersTo, which only exists in OpenJDK 16. Since layoutlib currently
uses JDK 11, this method needs to be implemented.

Bug: 74062470
Test: layoutlib tests
Change-Id: Ie7825605cc2b16e1f6de633646f43514c626fff4
2 files changed