Overlapping Navmeshes

[Elliebot-Z]

I'm unsure if there's a difference in severity between a navmesh overlapping itself versus two navmeshes overlapping each other. There must also exist a z-difference threshold where this no longer crashes.

[Noggog]

This may be rough to implement without getting super fancy, as we'll need to interpret navmesh data and do positional calculations or somesuch? We'll have to see once we dig in how rough it is. Good to have on the list, though