This commit introduces a banner on the "Start Export" modal
to notify the admin that their personal setting to export
private data is not toggled ON.
The banner is shown when the 'Export type' is 'Standard' and
admin's personal setting to export private data is not toggled ON.
The banner ensures admins are aware their private data will
not be exported unless they enable the respective setting.
Added a checkbox to toggle the option to automatically offer
to update the time zone with the browser time zone,
which is handled by the user profile field
"web_suggest_update_timezone".
A tooltip is also attached explaining the feature.
Fixes part of #16957
Removes deprecated `user` object from reactions objects returned by
the API as it is redundant because of the presence of `user_id` field in
the API and is not used by any clients now.
