Consider adding pathfinding tests

[lynxlynxlynx]

Fixing pathfinding bugs is quite tricky, but the core functions like FindPath are isolated and we could perhaps at least test for their correctness to make development easier. Static things like avoiding teleporting and pathing through walls, detecting overall path changes, should a bump occur etc.
I don't know if our test rig could easily handle it, but we'd also need to craft or reuse searchmap data.