[Bug] Generated mocks not accessible from within #Preview

You can't use a generated mock inside of a `#Preview`. The workaround is to use a preview `struct` that conforms to `PreviewProvider` instead, but it would be nice to be able to use `#Preview`.

Example:
```swift
@Mocked protocol Dependency {
    var value: Int { get }
}
   
   
// even in a new file
#Preview {
    let dependencyMock = DependencyMock() // not found
}
```