Add WanImage2ImagePipeline

[vladmandic]

Wan-AI/Wan2.2-T2V-A14B supported via WanPipeline is not only one of the best video models, its also widely popular as text-to-image model
(basically using it to produce video with single frame) due to its very good photo-realistic output.

Ask is to extend support by adding WanImage2ImagePipeline to allow image-to-image workflows
Work should be limited to setting timesteps and modifying prepare_latents method to take input image and strength params to encode input image and add noise to it, same as in pretty much any other image-to-image pipeline.

Note: this request is different than input image support in WanImageToVideoPipeline and WanVACEPipeline since

• a) those pipelines work with different model weights, so user cannot switch from text-to-image to image-to-image without full model reload
• b) they do not support denoising strength, image is taken as-is and if used in image-to-image workflow it will produce output identical to input.

Bonus: Also create WanInpaintPipeline to allow for image/mask combinations as input.

cc @yiyixuxu @sayakpaul @a-r-r-o-w @DN6