Use single dead annotation if entire module is unused

[sim642]

Running reanalyze https://github.com/rescript-association/reanalyze/commit/389dd682223201b42c33e5c444e5c79e0805adad on Goblint https://github.com/goblint/analyzer/commit/a544002114324a207df72f9e79eb656c3ebe7b5b revealed the following.

If an entire module is unused, then every single definition in the module is marked with a dead annotation (using -write at least). Although true, I think it's a bit too verbose. It would be neat if there could be just one annotation for the entire module.