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/internals/shared-key.js

@@ -0,0 +1,9 @@
+'use strict';
+var shared = require('../internals/shared');
+var uid = require('../internals/uid');
+
+var keys = shared('keys');
+
+module.exports = function (key) {
+  return keys[key] || (keys[key] = uid(key));
+};