Latent Diffusion Upscaler

I'd love to see the latent upscale model ported:
https://github.com/Stability-AI/stablediffusion#image-upscaling-with-stable-diffusion

The Unet architecture in x4-upscaling.yaml looks very similar to the Stable Diffusion model (v2-inference.yaml) so should be pretty straightforward but getting all the way to inferencing in Swift is a bit beyond my skill set. I'm more than willing to help and learn though.