Pixart with Controllnet

### Model/Pipeline/Scheduler description

Hello, thanks a lot for your great job.

However, I am wondering to use pixart with a extended constrain like controlnet's canny, but it seems that there is no such pipeline though shown on Pixart's github page. Will you plan to add this pipeline, or this will be proceeded after the release of Pixart's controlnet code?

### Open source status

- [ ] The model implementation is available.
- [ ] The model weights are available (Only relevant if addition is not a scheduler).

### Provide useful links for the implementation

_No response_

The issue does not name files, tests, or entry points. Start by reviewing the existing PixArt and ControlNet pipeline implementations in Diffusers, then determine whether a PixArt pipeline with ControlNet Canny support is still needed. Done would mean the requested pipeline is implemented and covered by appropriate tests.

Scritto dal modello di indicizzazione a partire dal testo della issue.