add custom sigmas and timesteps for StableDiffusionXLControlNet pipeline

[neuron-party]

What does this PR do?

adds custom sigmas and timesteps for StableDiffusionXLControlNet pipeline; users can specify these two arguments in the forward call in accordance with #7817.

Before submitting

• [] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Was this discussed/approved via a GitHub issue or the forum? Please add a link to it if that's the case. Link: pipe.scheduler.sigmas change after forward call #7904
• Did you make sure to update the documentation with your changes? Here are the
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• Did you write any new necessary tests?

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@yiyixuxu

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[yiyixuxu]

thank you!

[neuron-party]

will work on other pipelines too

[neuron-party]

@yiyixuxu #7963