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/lib0/json.js

@@ -0,0 +1,21 @@
+/**
+ * JSON utility functions.
+ *
+ * @module json
+ */
+
+/**
+ * Transform JavaScript object to JSON.
+ *
+ * @param {any} object
+ * @return {string}
+ */
+export const stringify = JSON.stringify
+
+/**
+ * Parse JSON object.
+ *
+ * @param {string} json
+ * @return {any}
+ */
+export const parse = JSON.parse