DotRecast creating tons of objects.

[bryanedds]

This is just for the small scene in TerraFirma -

Let's see if there's anything we or the maintainers of DotRecast can do to mitigate this.

[bryanedds]

If we can't directly improve the RcSpan object count, maybe instead of caching a reference of it we can cache a reference to the likely much lighter debug drawing info that we compute from it here -

https://github.com/bryanedds/Nu/blob/master/Nu/Nu/World/WorldFacets.fs#L3090-L3198

[bryanedds]

Solved our local issue with the new NavBuildResultData type.