FluxControlNetImg2ImgPipeline doesn't support generating more than one image

### Describe the bug

The FluxControlNetImg2ImgPipeline does not support generating more than one image.

The error encountered is: RuntimeError: Sizes of tensors must match except in dimension 1. Expected size 2 but got size 1 for tensor number 1 in the list.

I figured out that the control_mode needs to be sent as a list of control_mode values, matching the requested number of images specified by the num_images_per_prompt parameter.

As I see it, in the file pipeline_flux_controlnet_image_to_image.py, at line 818, the following code needs to be added:
if control_mode is not None:
if batch_size * num_images_per_prompt > 1:
control_mode = [control_mode] * batch_size * num_images_per_prompt
control_mode = torch.tensor(control_mode).to(device, dtype=torch.long)
control_mode = control_mode.reshape([-1, 1])

Does this make sense? Would you like PR on this fix?

### Reproduction

FluxControlNetImg2ImgPipeline with num_images_per_prompt=2

### System Info

diffusers = 0.32.2

### Who can help?

@sayakpaul @yiyixuxu

Beginne in pipeline_flux_controlnet_image_to_image.py ungefähr bei Zeile 818 und reproduziere den Fehler mit FluxControlNetImg2ImgPipeline unter Verwendung von num_images_per_prompt=2. Überprüfe die Behandlung von control_mode und stelle sicher, dass das Generieren von mehr als einem Bild nicht mehr den gemeldeten RuntimeError aufgrund einer Tensorgrößenabweichung auslöst.

Vom Indexierungsmodell aus dem Issue-Text verfasst.