Add test for rotation behavior with offset center of mass

[Jondolf]

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Rigid bodies should rotate around their center of mass, not around their Position. Rotating around the Position is unrealistic in cases where the center of mass is offset, and it can cause severe stability issues, as seen in for example #244 and #246.

#246 fixed the issue, but it would be good to have a test to make sure there are no behavior regressions in the future. I encountered this now with the solver rework (#385), as I accidentally made rotation ignore the center of mass again.