The KSampler from Fooocus as a ComfyUI node

On the surface basically two KSamplerAdvanced combined, therefore two input sets for base/refiner model and prompt.

• refiner_switch_step controls when the models are switched, like end_at_step/start_at_step with two discrete samplers.
• sharpness does some local sharpening with a gaussian filter without changing the overall image too much. Useful range seems to go up to 20 or so.

There is some magic beyond just encapsulating two samplers into one. This patches basic ComfyUI behaviour - don't use together with other samplers. Or perhaps do? Other samplers might profit from those changes ... ymmv.

It doesn't work ... Well, the example setup obviously does, at least for me. But anything nontrivial, like e.g. Controlnet and batch jobs, results in errors. I'd appreciate if somebody who actually understands the math would take a look at it