[9.18] Run the RPZ update as offloaded work (2-nd round)

Backport of !5938 (merged).

This MR is a revival of the reverted !6072 (merged).

The original commits from !6072 (merged) were slightly modified to fix cherry-pick conflicts with the current v9_18.

The shutdown issue, because of which the original MR was reverted, is expected to be fixed by !7516 (merged).

Closes #3190 (closed)