Rewrite Factorio server shutdown logic

Rewrite shutdown logic for Factorio servers to send a /quit command via
RCON for both Linux and Windows when stopping a server to avoid having
two confusingly intermixed code paths for Windows and Unix systems.
This makes shutdown on Windows tell clients the server shut down instead
of abruptly stoping to respond.

test/host/server.js

@@ -211,24 +211,28 @@ describe("host/server", function() {
 
 		describe(".stop()", function() {
 			it("should handle server quitting on its own during stop", async function() {
-				server.hangTimeoutMs = 20;
+				server.shutdownTimeoutMs = 20;
 				server._server = new events.EventEmitter();
 				server._server.kill = () => true;
 				server._state = "running";
-				server._rconReady = true;
+				server._rconReady = false;
 				server._rconClient = {
+					async sendRcon() { },
 					async end() {
 						server._rconClient = null;
-						process.nextTick(() => {
-							server.emit("_quitting");
-							server._server.emit("exit");
-						});
 					},
 				};
 				server._watchExit();
 
-				await server.stop();
-				await wait(21); // Wait until after hang timeout
+				const stop = server.stop();
+				stop.catch(() => {});
+				process.nextTick(() => {
+					server.emit("rcon-ready");
+					server._server.emit("exit");
+				});
+
+				await stop;
+				await wait(21); // Wait until after shutdown timeout
 			});
 		});
 	});