Fixed Xcode 27 beta build failures from outdated Swift package deployment targets

Tuist now uses correct deployment target floors when generating Swift package targets for Swift 6.4 / Xcode 27 beta. Previously, package targets could keep outdated minimums like iOS 12.0, which Xcode 27 rejects because it raised the supported deployment target range. Swift 6.4 packages now default to iOS 15.0, macOS 12.0, watchOS 9.0, tvOS 15.0, and visionOS 1.0, while Swift 5.9 packages keep the prior behavior. This fixes projects that failed to compile after upgrading to Xcode 27 beta due to external package targets falling below the supported range.