Track any fixes made to MONAI Generative during porting

[marksgraham]

While we are mid-port of MONAI Generative into MONAI Core, the Generative repo is active and people are still making bugfixes/PRs. This issue is to keep track of any fixes made on Generative on components that have already been ported to core. Once the Generative repo is frozen, these bug-fixes will be ported to core, and any new bug reports will be moved to the monai core repo.

1. Issue in reverse DDIM step fix here
2. Issue when initialising the PatchGAN discriminator with batchnorm in a distributed environment fix here
3. Issue where the save_intermediates flag was ignored in the inferer fix here
4. A helper function for loading in controlnet weights here and a fix to the controlnet inferer here
5. Allow inferer to take a quantized argument here