[Feature Request] Conditional execution control

Add nodes that allow to control the flow of execution i.e. conditional nodes that stop or change the execution path.
As it stands in, for example, with latent upscale workflow you have to manually connect or disconnect the nodes to enable/disable the upscaling. A node that stops execution based on a condition would allow to make a switch to turn parts of the graph on and off or divert the execution to a different path (i.e. latent upscale vs upscale with a model workflows).