dh_setup_copyright: Rework to improve metadata

Trying to properly support SBOM has been challenging, and even more when trying to address the issue with statically linked libraries. This MR aims to improve that by adding more logic at build time to properly compute paths and to generate license and copyright information.

Since this change will break compatibility with existing metadata it should be merged into v2026dev1.

Signed-off-by: Walter Lozano walter.lozano@collabora.com