[Core] Tear apart `from_pretrained()` of `DiffusionPipeline` (#8967)
* break from_pretrained part i.
* part ii.
* init_kwargs
* remove _fetch_init_kwargs
* type annotation
* dtyle
* switch to _check_and_update_init_kwargs_for_missing_modules.
* remove _check_and_update_init_kwargs_for_missing_modules.
* use pipeline_loading_kwargs.
* remove _determine_current_device_map.
* remove _filter_null_components.
* device_map fix.
* fix _update_init_kwargs_with_connected_pipeline.
* better handle custom pipeline.
* explain _maybe_raise_warning_for_inpainting.
* add example for model variant.
* fix