Cosmos3 Distilled support (#14177)
* Cosmos3 distilled support (dedicated modular pipeline + blocks)
* Address review comments
* Refactor unit test to use ModularPipelineTesterMixin
* Docs fix
* Tests refactor
* Pass generator to SDE scheduler for reproducibility
* Apply suggestion from @yiyixuxu
* Distilled text encoder step bugfix
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Co-authored-by: YiYi Xu <yixu310@gmail.com>
