memory leak fix attempt: store websockets and remove listeners when game ends (#1564)

## Description:

This is a temporary fix to remove websocket memory leaks.

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I have read and accepted the CLA aggreement (only required once).

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/server/GameServer.ts

@@ -61,6 +61,8 @@ export class GameServer {
   private kickedClients: Set<ClientID> = new Set();
   private outOfSyncClients: Set<ClientID> = new Set();
 
+  private websockets: Set<WebSocket> = new Set();
+
   constructor(
     public readonly id: string,
     readonly log_: Logger,
@@ -107,6 +109,7 @@ export class GameServer {
   }
 
   public addClient(client: Client, lastTurn: number) {
+    this.websockets.add(client.ws);
     if (this.kickedClients.has(client.clientID)) {
       this.log.warn(`cannot add client, already kicked`, {
         clientID: client.clientID,
@@ -401,10 +404,10 @@ export class GameServer {
   async end() {
     // Close all WebSocket connections
     clearInterval(this.endTurnIntervalID);
-    this.allClients.forEach((client) => {
-      client.ws.removeAllListeners();
-      if (client.ws.readyState === WebSocket.OPEN) {
-        client.ws.close(1000, "game has ended");
+    this.websockets.forEach((ws) => {
+      ws.removeAllListeners();
+      if (ws.readyState === WebSocket.OPEN) {
+        ws.close(1000, "game has ended");
       }
     });
     if (!this._hasPrestarted && !this._hasStarted) {