- properly embed navmesh saving and loading in SaveRestore flow
- use proper override save/load path if set
- use debugEx to not extract stackTrace when logging
- respect nav_disable convar
- fix empty tiles being null after loading from save, no tile should ever be null even if empty, this causes issue when queuing for rebuild at runtime
- consolidate redundant code paths into navmesh init, and add tile
- skip saving if navmesh was never built