Revert "Revert "workqueue: gut system_nrt[_freezable]_wq()""

This reverts commit 0c78723a3ac76095385595e9fb04d2b035dbf104.
Revert "Revert "System adapted to new workqueue 3.7""

This reverts commit 7a36143fc0a8cf6b51ee59359234bdae27481d3d.