add skip_layers argument to SD3 transformer model class (#9880)
* add skip_layers argument to SD3 transformer model class
* add unit test for skip_layers in stable diffusion 3
* sd3: pipeline should support skip layer guidance
* up
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Co-authored-by: bghira <bghira@users.github.com>
Co-authored-by: yiyixuxu <yixu310@gmail.com>