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/lodash/isNull.js

@@ -0,0 +1,22 @@
+/**
+ * Checks if `value` is `null`.
+ *
+ * @static
+ * @memberOf _
+ * @since 0.1.0
+ * @category Lang
+ * @param {*} value The value to check.
+ * @returns {boolean} Returns `true` if `value` is `null`, else `false`.
+ * @example
+ *
+ * _.isNull(null);
+ * // => true
+ *
+ * _.isNull(void 0);
+ * // => false
+ */
+function isNull(value) {
+  return value === null;
+}
+
+module.exports = isNull;