Rewrite WebSocket internals (#1410)

* Start rewriting Manager and Connection

* more stuff

* stuff

* Fix ready bug

* some stuff i forgot

* fix some stuff

* add stupid heartbeat ack like seriously who cares

* woo!

* fix a bug

* rate limit the dumb websocket

* stuff

* hdocs

* Docs

* Remove ClientManager#setupKeepAlive as it is now redundant

* Change Client._pingTimestamp to a getter that fetches the timestamp from the WebSocketConnection

* are you happy now eslint smh

* make gus happy

* Add CloseEvent external doc

* Make sure to emit 'reconnecting' when actually reconnecting

* ffs

* Fix RESUME logic

* Add heartbeat ack debug messages, including latency data

* Dumb stuff for Gus

* thx eslint

* more dumb stuff

* more dumb crap smh gus i h8 u

* moar messages

* fix for using wrong status, causing certain events not to be fired (#1422)

src/client/Client.js

@@ -156,13 +156,6 @@ class Client extends EventEmitter {
      */
     this.pings = [];
 
-    /**
-     * Timestamp of the latest ping's start time
-     * @type {number}
-     * @private
-     */
-    this._pingTimestamp = 0;
-
     /**
      * Timeouts set by {@link Client#setTimeout} that are still active
      * @type {Set<Timeout>}
@@ -182,6 +175,15 @@ class Client extends EventEmitter {
     }
   }
 
+  /**
+   * Timestamp of the latest ping's start time
+   * @type {number}
+   * @private
+   */
+  get _pingTimestamp() {
+    return this.ws.connection ? this.ws.connection.lastPingTimestamp : 0;
+  }
+
   /**
    * Current status of the client's connection to Discord
    * @type {?number}