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/symbol.js

@@ -0,0 +1,16 @@
+/**
+ * Utility module to work with EcmaScript Symbols.
+ *
+ * @module symbol
+ */
+
+/**
+ * Return fresh symbol.
+ */
+export const create = Symbol
+
+/**
+ * @param {any} s
+ * @return {boolean}
+ */
+export const isSymbol = s => typeof s === 'symbol'