[enhancement]: move controlnet preprocessing to separate handler

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Contact Details

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### What should this feature add?

Currently, ControlNet image preprocessing works by enqueuing a very small graph, with just a single controlnet processor node, to the front of the queue.

When other things are processing in the queue, it can take a while for your controlnet image to process, leading to an awkward user experience.

We should explore extracting the image processing logic in control images and exposing it outside of the graph execution system via the `utilities` router.

### Alternatives

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### Additional Content

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