Idempotency #386
Description
The idea we discussed some time ago was that the output of propagation could be an enum where the propagators declare whether they are idempotent or not. If the propagator is until the fixed point, we can avoid calling the propagator.
The question is whether this makes a difference for our current propagators. For problems with a lot of linear inequalities, this might make a difference. But since we also have incrementality for linear inequalities, it is not clear.