generate navmeshes on botclip surfaces

[illwieckz]

Please don't merge it, this only exists for discussion purpose.

[illwieckz]

This is an old commit sitting on my hard drive to generate navmeshes on botclip surface. While the navmeshes are properly generated, this can't work as a botclip in game because the playerclipping feature is based on contentparm and botclip is currently a surfaceparm.

On the other hand this can be a showcase of how we can do a material that can draw a navmesh out of thin air, even if it's not clipped.

This can have practical purpose like adding a fake navmesh border around boxes or disconnected islands with connect map around.

For example, with the well-known part of forlorn where bots land in diconnected islands that are large enough to not trigger the escape code, with such arbitrary navmesh extending outside of the actual surface, the bots would randomly roam outside of the island and fall in the map where they can then use a connected navmesh.

Another example would be the rope in hangar28 next human base, we may enforce daemonmap to generate a navmesh larger than what it does by default.

Anyway this is just an example of  “how to do it on daemonmap side”, please don't merge it until we know we want (and have a game-side implementation if required).

[illwieckz]

We may also want to reuse existing monsterclip contentparm (even if we name the material botclip) so we can implement it on game side without defining a new content parm, a monster (something we don't do), is very close to the concept of bot (opponent handled by the game, if I'm right).