FRE-600: Fix code review blockers

- Consolidated duplicate UndoManagers to single instance
- Fixed connection promise to only resolve on 'connected' status
- Fixed WebSocketProvider import (WebsocketProvider)
- Added proper doc.destroy() cleanup
- Renamed isPresenceInitialized property to avoid conflict

Co-Authored-By: Paperclip <noreply@paperclip.ing>

node_modules/core-js/modules/es.array.at.js

@@ -0,0 +1,20 @@
+'use strict';
+var $ = require('../internals/export');
+var toObject = require('../internals/to-object');
+var lengthOfArrayLike = require('../internals/length-of-array-like');
+var toIntegerOrInfinity = require('../internals/to-integer-or-infinity');
+var addToUnscopables = require('../internals/add-to-unscopables');
+
+// `Array.prototype.at` method
+// https://tc39.es/ecma262/#sec-array.prototype.at
+$({ target: 'Array', proto: true }, {
+  at: function at(index) {
+    var O = toObject(this);
+    var len = lengthOfArrayLike(O);
+    var relativeIndex = toIntegerOrInfinity(index);
+    var k = relativeIndex >= 0 ? relativeIndex : len + relativeIndex;
+    return (k < 0 || k >= len) ? undefined : O[k];
+  }
+});
+
+addToUnscopables('at');