Zombies path off edges, thinking space is walkable

[Peter0x44]

Describe the bug
In some circumstances when pathfinding, zombies can walk off ledges
To Reproduce
Steps to reproduce the behavior:
I tested on this custom map:
#997

1. /map Onewindows
2. walk behind the stamin-up perk machine
3. observe zombies will jump off the ledge to get to you

Expected behavior
zombies would walk around the ledge

Screenshots/Footage

noaudio_zombies.mp4

noaudio_dogs.mp4

Affected Platforms
I only tested fteqw, but I doubt it's specific

Additional context
This might be a problem if someone tried to create a map like the BO3 custom map octagonal ascention.
I'm not sure how actionable this with our current pathfinding system, maybe perhaps it can only be addressed with navmeshes.

Feel free to close if that's the case

supercedes #1038 #1039

[MotoLegacy]

@blubs Did your recent non-FTE path changes address something like this?