Modify calls to generative models diffusion model inferers to account for new inferer class

[virginiafdez]

Is your feature request related to a problem? Please describe.
This is a twin issue of: Project-MONAI/MONAI#8556.

Describe the solution you'd like
Diffusion model inferers class will move away from inferers.py. All the tutorials querying these will have to shift from the original inferers.py class to the new one.