Exposes a set of tiles for a [LayeredTileSet] resource.
Tiles in a source are indexed with two IDs, coordinates ID (of type Vector2i) and an alternative ID (of type int), named according to their use in the [LayeredTileSetAtlasSource] class.
Depending on the LayeredTileSet source type, those IDs might have restrictions on their values, this is why the base [LayeredTileSetSource] class only exposes getters for them.
You can iterate over all tiles exposed by a LayeredTileSetSource by first iterating over coordinates IDs using [method get_tiles_count] and [method get_tile_id], then over alternative IDs using [method get_alternative_tiles_count] and [method get_alternative_tile_id].
[b]Warning:[/b] [LayeredTileSetSource] can only be added to one LayeredTileSet at the same time. Calling [method LayeredTileSet.add_source] on a second [LayeredTileSet] will remove the source from the first one.