fix controlnet module refactor

[yiyixuxu]

#8768 breaks the legacy API for all controlnets it moved: flux, sd3, sdxl, sd, sparse;
e.g. docstring example for flux controlnet won't run on main https://huggingface.co/InstantX/FLUX.1-dev-Controlnet-Canny

this PR fixes that

[HuggingFaceDocBuilderDev]

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[yiyixuxu]

for models that inherits from ConfigMixin, it relies on its __init__ method signature to identify expected keys and only pass the expected keys to the model

diffusers/src/diffusers/configuration_utils.py

Line 465 in 99c0483

expected_keys = cls._get_init_keys(cls)

Currently with its signature being *args and **kwargs, None of the configs are being passed to the ControlNetModel when importing from this legacy location.

[yiyixuxu]

currently, you're getting a deprecation message like this - it is confusing because we are not deprecating ControlNetModel; we only deprecate importing from the previous file

FutureWarning: `ControlNetModel` is deprecated and will be removed in version 0.34. Importing `ControlNetModel` from `diffusers.models.controlnet` is deprecated and this will be removed in a future version. Please use `from diffusers.models.controlnets.controlnet import ControlNetModel`, instead.
  deprecate("ControlNetModel", "0.34", deprecation_message)

[yiyixuxu]

add MultiControlNetModel to top-level import because every other MultiControlNetModels are, e.g, SD3MultiControlNetModel, FluxMultiControlNetModel

[a-r-r-o-w]

Not sure if I've missed something, but the following changes look correctly done:

• Docstring fixes to correctly use ~models as opposed to ~diffusers or anything else.
• Init arguments are handled correctly as opposed to args and kwargs because otherwise our ConfigMixin won't work as expected.
• I've matched the default init parameters for all models and they seem to be the same as before [Core] introduce controlnet module #8768, so this looks correct.
• The deprecation messages are no longer ambiguous.
• MultiControlNetModel is now a top-level import accessible directly from diffusers.models but was not previously (or after [Core] introduce controlnet module #8768)
• Using cls.from_config as opposed to creating the class object directly from config is the preferred way to do things for from_* methods (?)

If these were all the intended changes, I think this is good to merge. With this PR, the linked Flux controlnet model works correctly as well, thanks!