[keras_hub/src/models/control_net] Add ControlNet

[SamuelMarks]

Originally implemented by Divum Gupta, then heavily modified by https://github.com/soten355 into MetalDiffusion.

Finally, I extracted out the TensorFlow variant and converted it to Keras 3.

TODO: test!

[sachinprasadhs]

Thanks for the PR.

Few general comments which needs to be addressed in this PR.

• Keep all the files under same model folder to maintain flat folder structure which we follow in Keras Hub
• Remove all ReadMe.md files, if the details are necessary, add it as part of docstring description.
• Use only absolute imports, no relative imports.
• Remove all the Copyright mentions.
• Remove KerasCV usage in the file names and in the class/method names.
• Keep the file names all lower case and avoid generic naming usage like layers.py, tools.py etc
• Follow functional model, refer to our usual design practice we follow for the models here https://github.com/keras-team/keras-hub/tree/master/keras_hub/src/models