doc: Clarify TileMap `world_to_map` and `map_to_world` usage
doc: Clarify TileMap `world_to_map` and `map_to_world` usage

Per discussion in #38551.
Fixes #31663.
Fixes #37394.

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot