For both TileMap and GridMap:
- `world_to_map` -> `local_to_map`
- `map_to_world` -> `map_to_local`
Also changes any mention of "world" in this context to "local" to avoid future confusion.
Finally, updates the docs of both methods for consistency.
In particular, adding a note on how to convert the returned values from local to global coordinates and vice versa.