Consider adding drain method to TileStorage

[rparrett]

I'd like to be able to easily despawn all the tiles in a tilemap without putting them in a Bevy hierarchy.

Also, it would be nice if remove returned the removed entity, if there was one.

[ChristopherBiscardi]

feels like drain makes sense. Have to set all drained items to None and probably only return the Entitys. So probably a bunch of removes with the change would do it simply enough.

we can easily return the entity from remove. it's already a take, so we just remove the semicolon and add the return value.