Add FSDP option for Flux2 (#12860)
* Add FSDP option for Flux2
* Apply style fixes
* Add FSDP option for Flux2
* Add FSDP option for Flux2
* Add FSDP option for Flux2
* Add FSDP option for Flux2
* Add FSDP option for Flux2
* Update examples/dreambooth/README_flux2.md
* guard accelerate import.
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Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
