Registry Swift packages load without a local Package.swift manifest

Projects using Swift Package Manager dependencies from a registry now build correctly. Tuist previously treated a missing Package.swift manifest as a stale cache entry and fell back to the manifest loader, which could fail for registry packages that ship without manifests. The package info cache now keeps the cached info when the package comes from a registry and no manifest is present, avoiding unnecessary reloads and build failures. Swift packages loaded from local paths still validate against the on-disk Package.swift as before.