Add StableDiffusion3PAGImg2Img Pipeline + Fix SD3 Unconditional PAG (#9932)

* fix progress bar updates in SD 1.5 PAG Img2Img pipeline

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Co-authored-by: Vinh H. Pham <[email protected]>
Co-authored-by: Sayak Paul <[email protected]>

Author: 3 people

src/diffusers/__init__.py

@@ -346,6 +346,7 @@
             "StableDiffusion3InpaintPipeline",
             "StableDiffusion3PAGImg2ImgPipeline",
             "StableDiffusion3PAGPipeline",
+            "StableDiffusion3PAGImg2ImgPipeline",
             "StableDiffusion3Pipeline",
             "StableDiffusionAdapterPipeline",
             "StableDiffusionAttendAndExcitePipeline",