Convert list/tuple of `SD3ControlNetModel` to `SD3MultiControlNetModel` (#9652)

Convert list/tuple of SD3ControlNetModel to SD3MultiControlNetModel
Co-authored-by: YiYi Xu <yixu310@gmail.com>

src/diffusers/pipelines/controlnet_sd3/pipeline_stable_diffusion_3_controlnet.py

@@ -192,6 +192,8 @@ class StableDiffusion3ControlNetPipeline(DiffusionPipeline, SD3LoraLoaderMixin,
         ],
     ):
         super().__init__()
+        if isinstance(controlnet, (list, tuple)):
+            controlnet = SD3MultiControlNetModel(controlnet)
 
         self.register_modules(
             vae=vae,