Introduce system_modules property to java_api_library

System_modules property provides the jars passed as bootclasspath when
compiling the stubs in the java_api_library where its creating
java_sdk_library's sdk_version is none, as the jars will not be provided
from the full_surface_stub_libs but compiled by itself in the child
change.

The jar provided by the system_modules will also be passed to metalava
to resolve hierarchy coming from outer dependencies.

Test: m --build-from-text-stub
Bug: 288624417
Change-Id: I8f3b89efa24bceb070d7a37fae3c7334dd7f0868