SwiftPM C-family target headers now surface in generated projects

Generated Xcode projects now expose C-family SwiftPM target headers the same way SwiftPM classifies them: every header under the target’s public headers directory is exposed as a Public header (recursively, including h/hh/hpp/h++/hp/hxx/H/ipp/def), and other headers in the target are exposed as Project headers. Targets with custom module maps, umbrella headers, and nested include directories now work in tuist generate, unblocking integration of packages such as OpenSwiftUI.