Compile android.test.*.stubs into dex

Adjust the build rules of android.test.*.stubs packages to also
produce a jar with dex files. This will be used by the `hiddenapi`
tool to categorize the boot class path equivalents as public API.

Bug: 79409988
Test: m android.test.base.stubs ; check javalib.jar contains dex
Change-Id: I1d0850b18044c559ea4b9893d929dc45884b32c3