Add cos xl

[GavChap]

Description

• Add support for cosxl and other vpred EDM checkpoints
• Added code to sort the above

Cos Stable Diffusion XL (CosXL) 1.0 Base is tuned to use a Cosine-Continuous EDM VPred schedule. The most notable feature of this schedule change is its capacity to produce the full color range from pitch black to pure white, alongside more subtle improvements to the model's rate-of-change to images across each step.

This improves the colour range considerably over SDXL.

A few models are available on CivitAI at the following link: https://civitai.com/search/models?sortBy=models_v9&query=CosXL The official model is here: https://huggingface.co/stabilityai/cosxl

Download a model and place it in the normal checkpoint directory and use it as a normal model, no settings changes needed as it's detected by the code change below.

Example output

Checklist:

• [x] I have read contributing wiki page
• [x] I have performed a self-review of my own code
• [x] My code follows the style guidelines
• [x] My code passes tests

[GavChap]

Can you add a short summary of how to use this new feature? e.g. where to download checkpoints, and steps with screenshots of GUI to use the feature.

Done.