GitLab

* Improve dynamic threshold

* Update code

* Add dynamic threshold to ddim and ddpm

* Encapsulate and leverage code copy mechanism

Update style

* Clean up DDPM/DDIM constructor arguments

* add test

* also add to unipc

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Co-authored-by: Peter Lin <peterlin9863@gmail.com>
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>