Copy lora functions to XLPipelines (#4512)
* add load_lora_weights and save_lora_weights to StableDiffusionXLImg2ImgPipeline
* add load_lora_weights and save_lora_weights to StableDiffusionXLInpaintPipeline
* apply black format
* apply black format
* add copy statement
* fix statements
* fix statements
* fix statements
* run `make fix-copies`
