There are only a couple SDXL inpainting models, and my tests indicate they are not as good as SD1.5 inpainting, but at least we support them now.
- Add the config file. This matches what is used in A1111. The only difference from the non-inpainting SDXL config is the number of in-channels.
- Update the legacy config maps to use this config file.
- Use the our adaptation of the HWC3 function with better types
- Extraction some of the util functions, name them better, add comments
- Improve type annotations
- Remove unreachable codepaths
## Summary
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## Checklist
- [ ] _The PR has a short but descriptive title, suitable for a
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- [ ] _Tests added / updated (if applicable)_
- [ ] _Documentation added / updated (if applicable)_
- Shift+C: Reset selected layer mask (same as canvas)
- Shift+D: Delete selected layer (cannot be Del, that deletes an image in gallery)
- Shift+A: Add layer (cannot be Ctrl+Shift+N, that opens a new window)
- Ctrl/Cmd+Wheel: Brush size (same as canvas)
