Update swiftui template

[ezraberch]

Short description 📝

The current swiftui template isn't functional out-of-the-box; while it will build and run, running the generated project will not display the "Hello, World!" from the SwiftUI view. It is also not fully SwiftUI.

This PR revamps the template, using the default Xcode template as a base. Additionally, in doing so I discovered that using .directory() in a template does not work under certain conditions, so this has been fixed. Like the existing template, the new template supports macOS, iOS, and tvOS.

Checklist ✅

• The code architecture and patterns are consistent with the rest of the codebase.
• The changes have been tested following the documented guidelines.
• The CHANGELOG.md has been updated to reflect the changes. In case of a breaking change, it's been flagged as such.
• In case the PR introduces changes that affect users, the documentation has been updated.
• In case the PR introduces changes that affect how the cache artifact is generated starting from the TuistGraph.Target, the Constants.cacheVersion has been updated.

[fortmarek]

Tested locally and works great, thanks @ezraberch 👏