Improve pathfinding

[Fris0uman]

• Use NavigationServer2D as advised
• Add small logic to have robots path around each other after colliding, it works but if too many robots get into the pile they still get stuck
• Use collision layers instead of checking the class of the collider
• Edit the map a bit to remove case that the pathfinding can't handle
• Chnage how robots wnader so that they'll explore in every direction from the depot