Collect aconfig files from *_libs in java_api_library

Aconfig files can be provided to java_api_library in two ways:
1. By specifying the aconfig_declarations module names in the
   aconfig_declarations property

2. By specifying the java_aconfig_library (or its static rdeps) module
   names in the libs/static_libs property

1. was behaving as expected for java_api_library, but 2. was not
behaving as expected and java_api_library is erroneously not collecting
the aconfig files from the libs/static_libs dependencies. This change
fixes such broken behavior.

Test: CI
Bug: 379807097
Change-Id: I1d6d1fa4eae32b4f28e68c88e4e67b2ff7ae7805