New sampler: UniPC - Unified Predictor-Corrector Framework for Fast Sampling

[catboxanon]

UniPC: A Unified Predictor-Corrector Framework for Fast Sampling of Diffusion Models

Paper: https://arxiv.org/abs/2302.04867
Project page: https://unipc.ivg-research.xyz
GitHub: https://github.com/wl-zhao/UniPC

---

I took a crack at implementing it but the webui's way of hijacking into samplers doesn't make it very clear how to go about adding a new one. Posting here incase someone else more familiar with the webui code is interested in implementing it. The project page mentions the UniC portion can be applied after any DPM sampler as well.

[space-nuko]

Implemented here: #7710