[Core] introduce `controlnet` module (#8768)
* move vae flax module.
* controlnet module.
* prepare for PR.
* revert a commit
* gracefully deprecate controlnet deps.
* fix
* fix doc path
* fix-copies
* fix path
* style
* style
* conflicts
* fix
* fix-copies
* sparsectrl.
* updates
* fix
* updates
* updates
* updates
* fix
---------
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>
