More ham-sandwich levels

[SanderBeekhuis]

Ideally add a few more levels to the Ham Sandwich problem (also, in some
problems you are allowed way more swaps than necessary. Is that
intentional?)

[SanderBeekhuis]

We currently have 9 levels, I would say that is about enough without becoming repetetive.

[kbuchin]

I think the best would be random level generation as we have for "connect". Generating levels without swaps is easy (with swaps shouldn't be much more complicated, but we can keep it simple).