[InstructPix2Pix] Fix pipeline implementation and add docs (huggingface#4844)

* initial evident fixes.

* instructpix2pix fixes.

* add: entry to doc.

* address PR feedback.

* make fix-copies

Author: sayakpaul

docs/source/en/api/pipelines/pix2pix.md

@@ -35,4 +35,12 @@ Make sure to check out the Schedulers [guide](/using-diffusers/schedulers) to le
 	- save_lora_weights
 
 ## StableDiffusionPipelineOutput
-[[autodoc]] pipelines.stable_diffusion.StableDiffusionPipelineOutput
+[[autodoc]] pipelines.stable_diffusion.StableDiffusionPipelineOutput
+
+## StableDiffusionXLInstructPix2PixPipeline
+[[autodoc]] StableDiffusionXLInstructPix2PixPipeline
+	- __call__
+	- all
+
+## StableDiffusionXLPipelineOutput
+[[autodoc]] pipelines.stable_diffusion_xl.StableDiffusionXLPipelineOutput