Multi-controlnet batching for `StableDiffusionXLControlNetInpaintPipeline`

**Is your feature request related to a problem? Please describe.**
Currently, batching is not supported when we are conditioning the SDXL pipeline on multiple controlnets: https://github.com/huggingface/diffusers/blob/28f9d84549c0b1d24ef00d69a4c723f3a11cffb6/src/diffusers/pipelines/controlnet/pipeline_controlnet_inpaint_sd_xl.py#L771

**Describe the solution you'd like.**
We can pass a list of lists of images for batch inference.

**Describe alternatives you've considered.**
One-by-one processing, which results in very low GPU utilization.

There was a similar PR raised for the `StableDiffusionControlNetPipeline` https://github.com/huggingface/diffusers/pull/6334

Empieza en src/diffusers/pipelines/controlnet/pipeline_controlnet_inpaint_sd_xl.py, en la lógica de batching mencionada. Compara la entrada solicitada de tipo list-of-lists con el cambio similar en StableDiffusionControlNetPipeline del PR #6334. Se considera terminado cuando la inferencia de inpainting con multi-ControlNet SDXL acepta entradas en batch y evita procesarlas una por una.

Escrito por el modelo de indexación a partir del texto del issue.