Add support and tests for export_*_lib_headers

There are 3 different properties about exporting headers in Soong:

1. export_static_lib_headers
2. export_shared_lib_headers
3. export_header_lib_headers

The static and header cases are already supported in bp2build but
do not have tests. This CL adds support for the shared case and
adds tests for all cases.

Fixes: 236268577
Test: Unit tests
Change-Id: Idfb788271e607919d4ac6bc0e4eb4e6ff8f78e8d