SwiftPM warning control settings now supported in generated projects

Generated Xcode projects now recognize SwiftPM warning control target build settings (treatAllWarnings, treatWarning, and enableWarning) that newer packages emit. The settings are decoded and lowered into OTHER_SWIFT_FLAGS, OTHER_CFLAGS, and OTHER_CPLUSPLUSFLAGS the same way SwiftPM itself does, so the package author’s warning behavior is preserved: -warnings-as-errors / -Werror= / -W and their negatives are applied per language. This unblocks loading packages like swift-dependencies 1.13.0, which previously failed Tuist’s PackageInfo decoding before the graph could be mapped.