Postprocessing refactor img2img (#3268)
* refactor img2img VaeImageProcessor.postprocess
* remove copy from for init, run_safety_checker, decode_latents
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>
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Co-authored-by: yiyixuxu <yixu@yis-macbook-pro.lan>
Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>
