VoiceConnection rework (#1183)

* VoiceConnection rework

- improves codebase
- removes concept of pending connections
- attempts to fix memory leaks by removing EventEmitter listeners
- makes voice connections keep track of its own channel when it is moved by another user
- allows voice connections to reconnect when Discord falls back to another voice server or a region change occurs
- adds events for some of the aforementioned events

* Removed unused code

* More clean up / bugfixes

* Added typedefs to Status and VoiceStatus constants

src/util/Constants.js

@@ -163,6 +163,16 @@ const Endpoints = exports.Endpoints = {
   emoji: (emojiID) => `${Endpoints.CDN}/emojis/${emojiID}.png`,
 };
 
+/**
+ * The current status of the client. Here are the available statuses:
+ * - READY
+ * - CONNECTING
+ * - RECONNECTING
+ * - IDLE
+ * - NEARLY
+ * - DISCONNECTED
+ * @typedef {number} Status
+ */
 exports.Status = {
   READY: 0,
   CONNECTING: 1,
@@ -172,6 +182,23 @@ exports.Status = {
   DISCONNECTED: 5,
 };
 
+/**
+ * The current status of a voice connection. Here are the available statuses:
+ * - CONNECTED
+ * - CONNECTING
+ * - AUTHENTICATING
+ * - RECONNECTING
+ * - DISCONNECTED
+ * @typedef {number} VoiceStatus
+ */
+exports.VoiceStatus = {
+  CONNECTED: 0,
+  CONNECTING: 1,
+  AUTHENTICATING: 2,
+  RECONNECTING: 3,
+  DISCONNECTED: 4,
+};
+
 exports.ChannelTypes = {
   text: 0,
   DM: 1,