### Godot version

4.01

### System information

Windows 10

### Issue description

It seems a tiles Custom Data is cleared/not set when "Local to Scene" is enabled for the TileMap in the Resource section. At least the custom data isn't set by the time of the _ready function in the script attached to the TileMap.

### Steps to reproduce

create TileMap and tileset with custom data and attached script. in _ready method attempt to read custom data from a used cell. 

In Attached project run it. It will print_debug if it found custom data or not. "Local to Scene" is enabled so it will not find the custom data.

### Minimal reproduction project

[TileMapCustomDataLocalBugReproduce.zip](https://github.com/godotengine/godot/files/11470771/TileMapCustomDataLocalBugReproduce.zip)

if (custom_data_layers_by_name.has(p_value)) {
		return custom_data_layers_by_name[p_value];
	} else {
		return -1;
	}
}
void TileSet::set_custom_data_layer_name(int p_layer_id, String p_value) {
	ERR_FAIL_INDEX(p_layer_id, custom_data_layers.size());
	
	if (!p_value.is_empty()) {
		for (int other_layer_id = 0; other_layer_id < get_custom_data_layers_count(); other_layer_id++) {
			if (other_layer_id != p_layer_id && get_custom_data_layer_name(other_layer_id) == p_value) {
				ERR_FAIL_MSG(vformat("There is already a custom property named %s", p_value));
			}
		}
	}
	if (p_value.is_empty() && custom_data_layers_by_name.has(p_value)) {
		custom_data_layers_by_name.erase(p_value);
	} else {
		custom_data_layers_by_name[p_value] = p_layer_id;
	}
	custom_data_layers.write[p_layer_id].name = p_value;
	emit_changed();
}
String TileSet::get_custom_data_layer_name(int p_layer_id) const {