Without actually simulating cluster implementation at all. Instead, only
the essential fact that cluster gateways know what changes they have
made to each node of a cluster. That is enough for sims like
sizebalanced_cluster.
The generator doesn't emit the best possible connect commands,
but it does output something valid. Eg, an input like:
connect A <-> B <-> C <-> D
becomes:
connect A <-> B <-> C
connect C <-> D
Also:
connect A -> B <- C
becomes:
connect A -> B
connect C -> B
Which could be improved.
Also disconnect commands are not prettified at all, but probably there's
no reason to.
