transitive Java deps for r8

The -libraryjars argument to r8 was missing transitive dependencies, and
so complained when there were classes used in the program JAR which were
not provided via libraries. This CL propagates transitive dependencies
to the r8 command to reduce the warnings that are generated for missing classes.

Bug: 242088131
Change-Id: Ifad7bc7c5d406e3de8d98ea963c97e88c84b45a1