SwiftPM C-family target headers are included in generated projects

When generating projects that integrate SwiftPM C-family targets, Tuist now includes the target’s headers in the generated project with the same public/project classification SwiftPM uses. Public headers (everything under the target’s public headers directory, matched recursively) are marked as public, and all other headers are treated as project headers. This applies across custom module maps, umbrella headers, and generated module maps, and supports nested and non-.h headers such as .hpp and .hxx. It also respects the SwiftPM target’s exclude paths so headers under excluded paths are not included. Swift-only targets are unaffected.