master-1c168d9

fix: repair flash attention support (#386)

* repair flash attention in _ext
this does not fix the currently broken fa behind the define, which is only used by VAE

Co-authored-by: FSSRepo <FSSRepo@users.noreply.github.com>

* make flash attention in the diffusion model a runtime flag
no support for sd3 or video

* remove old flash attention option and switch vae over to attn_ext

* update docs

* format code

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Co-authored-by: FSSRepo <FSSRepo@users.noreply.github.com>
Co-authored-by: leejet <leejet714@gmail.com>