[Feature] Support PixArt DreamBooth Style

[okotaku]

Motivation

ZipLoRA: Any Subject in Any Style by Effectively Merging LoRAs
SDXL model learns to produce stylized outputs when fine-tuned on a single example of a reference style using LoRA with a DreamBooth objective.

Apply it to PixArt.

Results (Optional)

pixart_alpha_1024_dreambooth_lora_cat_waterpainting

Checklist

Before PR:

• Pre-commit or other linting tools are used to fix the potential lint issues.
• Bug fixes are fully covered by unit tests, the case that causes the bug should be added in the unit tests.
• The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• The documentation has been modified accordingly, like docstring or example tutorials.

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📚 Documentation preview 📚: https://DiffEngine--108.org.readthedocs.build/en/108/