Add manual extractor resource transfers

tests/_extractor_transfer_preview.gd

@@ -0,0 +1,24 @@
+extends Node2D
+
+
+func _ready() -> void:
+	GameState.extractors.clear()
+	GameState.transporters.clear()
+	GameState.fleet_cargo = 9
+	GameState.fleet_gas_cargo = 4
+	var main: Node = load("res://Main.tscn").instantiate()
+	add_child(main)
+	var planet: Node2D
+	for planets in main.get_node("PlanetField").populated_chunks.values():
+		if not planets.is_empty() and is_instance_valid(planets[0]):
+			planet = planets[0]
+			break
+	if planet == null:
+		return
+	GameState.add_extractor(planet.planet_name, planet.position, planet.resource_type, planet.planet_id)
+	var index: int = GameState.extractors.size() - 1
+	GameState.extractors[index].inventory.deposit(planet.resource_type, 38)
+	var controller: Node = main.get_node("BuildController")
+	controller.transfer_extractor_index = index
+	main.get_node("UI/TransferMenu").visible = true
+	controller._refresh_transfer()