Animatediff Proposal (#5413)
* draft design
* clean up
* clean up
* clean up
* clean up
* clean up
* clean up
* clean up
* clean up
* clean up
* update pipeline
* clean up
* clean up
* clean up
* add tests
* change motion block
* clean up
* clean up
* clean up
* update
* update
* update
* update
* update
* update
* update
* update
* clean up
* update
* update
* update model test
* update
* update
* update
* update
* make style
* update
* fix embeddings
* update
* merge upstream
* max fix copies
* fix bug
* fix mistake
* add docs
* update
* clean up
* update
* clean up
* clean up
* fix docstrings
* fix docstrings
* update
* update
* clean up
* update
