[Core] Improve `.to(...)` method, fix offloads multi-gpu, add docstring, add dtype (#5132)
* fix cpu offload
* fix
* fix
* Update src/diffusers/pipelines/pipeline_utils.py
* make style
* Apply suggestions from code review
Co-authored-by: YiYi Xu <yixu310@gmail.com>
Co-authored-by: Pedro Cuenca <pedro@huggingface.co>
* fix more
* fix more
---------
Co-authored-by: YiYi Xu <yixu310@gmail.com>
Co-authored-by: Pedro Cuenca <pedro@huggingface.co>