Cache static and dynamic library targets as binary XCFrameworks

Static and dynamic library targets can now be cached as binary XCFrameworks in the module cache. Cache warm creates library XCFrameworks with xcodebuild -create-xcframework -library, preserves public headers and Swift module directories, and restores them into the generated project so mixed framework and library graphs reuse the same binary cache pipeline. The Module Cache guide and changelog have been updated with library support details.