Collision or physics integration

I don't know exactly how this would be implemented but maybe having first class support for BVH and other data structures used by physics/collision engines would be great. Maybe a parry3d and parry2d integration since those are the backbone of many physics engines and just handle collisions.

I ran some experiments with collision / physics and it is quite expensive to do the "normal way"... with massive amounts of optimization and trade offs its feasible but still doesn't seem worth it in spacetime when a side car can do the trick.

Speaking of sidecars, maybe just add first-class support for side cars so we can deploy all in one? Anyway, I'd personally like collision - physics would be cool but isn't needed by like 98% of games - and ideally the feature makes it financially viable to use in a real time game.

Requested by @onx2 via the SpacetimeDB site.

The issue names no files, tests, or entry points. Start by surveying how SpacetimeDB currently supports sidecars and external integrations, then assess the proposed parry3d/parry2d, BVH, and collision or physics scope; the issue is complete only once a concrete, agreed integration design and measurable real-time performance target are defined.