Ensure that <x>-hiddenapi modules are included in hiddenapi-index.csv

Adds a test that makes sure that <x>-hiddenapi modules that provide
additional annotations for the <x> boot jar module are included when
generating the hiddenapi-index.csv file.

Bug: 178361284
Test: m nothing
Change-Id: I866916c9275af17954e0634347d183228d4ddc17