Add ExperimentalSidebarPreference in the config (#9013)

* Add ExperimentalSidebarPreference in the config

* Override Sidebar preference based on GroupUnread settings

* Rename to ExperimentalChannelOrganization

* Add Sidebar config in diagnostics

* Fix diagnostics for experimental_channel_organization

config/default.json

@@ -63,6 +63,7 @@
         "EnableTutorial": true,
         "ExperimentalEnableDefaultChannelLeaveJoinMessages": true,
         "ExperimentalGroupUnreadChannels": "disabled",
+        "ExperimentalChannelOrganization": false,
         "ImageProxyType": "",
         "ImageProxyOptions": "",
         "ImageProxyURL": "",