Add static_libs property in java_api_library soong module

Package private stub annotations are not part of any API surfaces, but
are included in the `android_<API_SURFACE_NAME>_stubs_current`. Since
these cannot be included in the java_api_library by api_contributions,
add static_libs property to statically include jars in the output jar
file.

Test: m
Change-Id: Icb4401f29079ba32df4c192943a7e8814599d9ba