Before this commit, mail status manager was regularly fetching `im_status` of partners with `this._rpc()`. This used the main thread worker, so it may be overloaded because of that. To mitigate this issue, mail status manager now uses a new route `/longpolling/im_status` to fetch `im_status` of partners using the longpolling thread worker. closes odoo/odoo#33238 Signed-off-by: Olivier Dony (odo) <odo@openerp.com>