Add start_at_step end_at_step to presampling custom?

[holyspidoo]

To use an optional_sampler (example: detail daemon), I switched from PreSampling Advanced to PreSampling Custom node. But I lose the start_at_step/end_at_step options.

My workaround is to use optional sigmas with SplitSigmas node to get the same effect, but it would be more clean to have the options directly in the PreSampling Custom node.