java_sdk_library_import - expose system and test stubs

Previously, the java_sdk_library_import only exposed the public stubs.
This change adds support for exposing system and test stubs too by adding
separate structures for public, system and test scopes. The existing
properties are kept for legacy reasons (and because libs can be common
across the differents scopes).

It extracts some code that is common to both sdk library and sdk
library import.

The legacy support will be removed in a future change once all existing
usages have been switched over.

Bug: 148080325
Test: m droid
      TARGET_BUILD_APPS=Camera2 m
Change-Id: I0b26cc8af9ee044437ff3b80c1eca611816b9386