Fix UniPC data cast and shape broadcast in #184
This also fix potential problems in DDIM. The cause of this BUG is A1111’s `modules\models\diffusion\uni_pc\uni_pc.py` does not have a data cast and the Forge’s DDIM estimator forget to match the broadcast shape of sigmas.
(At the same time when we are fixing this BUG in A1111’s very original and high-quality samplers, comfyanonymous is still believing that Forge is using comfyui to sample images, eg, ComfyUI UniPC.
Comfyanonymous is so cute.
See also the jokes here https://github.com/lllyasviel/stable-diffusion-webui-forge/discussions/169#discussioncomment-8428689)
Allows loading instruct-pix2pix models via same method as inpainting models in sd_models.py and sd_hijack_ip2p.py
Adds ddpm_edit.py necessary for instruct-pix2pix