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/level-concat-iterator/index.js

@@ -0,0 +1,15 @@
+module.exports = function (iterator, cb) {
+  var data = []
+  var next = function () {
+    iterator.next(function (err, key, value) {
+      if (err || (key === undefined && value === undefined)) {
+        return iterator.end(function (err2) {
+          cb(err || err2, data)
+        })
+      }
+      data.push({ key: key, value: value })
+      next()
+    })
+  }
+  next()
+}