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/array-buffer-non-extensible.js

@@ -0,0 +1,11 @@
+'use strict';
+// FF26- bug: ArrayBuffers are non-extensible, but Object.isExtensible does not report it
+var fails = require('../internals/fails');
+
+module.exports = fails(function () {
+  if (typeof ArrayBuffer == 'function') {
+    var buffer = new ArrayBuffer(8);
+    // eslint-disable-next-line es/no-object-isextensible, es/no-object-defineproperty -- safe
+    if (Object.isExtensible(buffer)) Object.defineProperty(buffer, 'a', { value: 8 });
+  }
+});