6676 port generative networks controlnet (#7312)

Part of #6676  .

### Description

Ports the ControlNet.

### Types of changes
<!--- Put an `x` in all the boxes that apply, and remove the not
applicable items -->
- [x] Non-breaking change (fix or new feature that would not break
existing functionality).
- [ ] Breaking change (fix or new feature that would cause existing
functionality to change).
- [x] New tests added to cover the changes.
- [ ] Integration tests passed locally by running `./runtests.sh -f -u
--net --coverage`.
- [ ] Quick tests passed locally by running `./runtests.sh --quick
--unittests --disttests`.
- [x] In-line docstrings updated.
- [x] Documentation updated, tested `make html` command in the `docs/`
folder.

---------

Signed-off-by: Mark Graham <[email protected]>

Author: marksgraham

docs/source/networks.rst

@@ -588,6 +588,11 @@ Nets
 .. autoclass:: DiffusionModelUNet
   :members:
 
+`ControlNet`
+~~~~~~~~~~~~
+.. autoclass:: ControlNet
+  :members:
+
 `RegUNet`
 ~~~~~~~~~
 .. autoclass:: RegUNet

monai/networks/nets/__init__.py

@@ -18,6 +18,7 @@
 from .basic_unet import BasicUNet, BasicUnet, Basicunet, basicunet
 from .basic_unetplusplus import BasicUNetPlusPlus, BasicUnetPlusPlus, BasicunetPlusPlus, basicunetplusplus
 from .classifier import Classifier, Critic, Discriminator
+from .controlnet import ControlNet
 from .daf3d import DAF3D
 from .densenet import (
     DenseNet,