Add a test for hidden API encoding of java_sdk_library

Fill a hole in the testing of hidden API encoding. Some comments in the
code indicate that the child implementation java_library of a
java_sdk_library should have hidden API flags encoded in its dex jar
just like the embedded java_library. However, this test proves that it
is not working. This will be fixed in a follow up change.

Bug: 179354495
Test: m nothing
Change-Id: Ia581a17f1e48dff252d17f16bf76adf039f46b60