Clean up xcframework header and module map paths

Two related fixes clean up the cached xcframework header and module map paths. Targets that link a precompiled xcframework that ships its own module.modulemap no longer see a second copy of the module on HEADER_SEARCH_PATHS, which was producing redefinition of module 'X'. Static framework targets also no longer receive copied product-level module maps that could expose the same Objective-C module map through two paths in archive topologies. Module-map-less xcframeworks (the cached Swift/library products from the module cache work) still receive their headers unchanged.