Following the AI unthreading in rP26274 / D3769, we can actually stop using structured clones to pass the gamestate around. This is much, much faster. On a simple AI 1v1, I get around a 15% raw speed boost. This will go down as we add more AIs, but overall it's a great change.
Further side-effects: writing clones allocated a ton of temporary data, so this probably helps significantly with memory fragmentation.
Further work: we probably don't need to reset everything every turn, which would help the GC.
