Add latent upscale

[Warvito]

A possible new feature to support described in AUTOMATIC1111/stable-diffusion-webui#5521 and huggingface/diffusers#2059 . Instead upscaling atthe image level, we can perform upscaling at the latent space level. This might help to save memory when working with even higher image resolutions

https://github.com/Hosiokaa/Latent-Space-Upscaling-Guide-