Progress measures for diffusion simulations

Currently we only measure how much time progressed in 125k traces that we analyse, but this is not good enough measure of progress for diffusion. We should label each simulation run with:

* the tip of the chain of each node, i.e. `(slotNo, blockNo, and hash) `; and present it in a comprehensible way
* the intersection point of all the chains, i.e. `(slotNo, blockNo)`.