Vessel destruction is expensive

[pleroy]

While replaying the journal for #3375, I am noticing that destroying a vessel is rather expensive (in some cases, 20-30 seconds). I have not investigated why, but I suspect that the vessels that are slow to destroy have tons of checkpoints. We might want to address this note sooner rather than later. Or we might want to put the vessel in an arena. Or both.

[pleroy]

Note that #3385 addressed most of the problem. An arena might still make sense, but it would add code complexity.

[pleroy]

Arenas don't work well with STL or absl containers, so nothing left to do here.