Support SwiftPM warning control settings

Package.swift files that use SwiftPM’s newer warning-control APIs (treatAllWarnings, treatWarning, enableWarning) used to fail Tuist’s PackageInfo decoding before the package could be mapped into Xcode projects. Those settings are now decoded and mapped to the same OTHER_SWIFT_FLAGS, OTHER_CFLAGS, and OTHER_CPLUSPLUSFLAGS flags that SwiftPM uses, so packages such as swift-dependencies 1.13.0 load cleanly and the package author’s warning configuration reaches the generated Xcode projects. Unsupported combinations (linker warning-control settings, Swift enableWarning) are still rejected with a clear error.