refactor(run-engine): share one copy of the remaining ck lua

Finishes what the ack, nack and dead-letter commit started. The two enqueue
commands, the TTL sweep and the dequeue are each written once now, with named
slots the two builds fill differently.

Most slots are insertion points the virtual-time build adds to and the flag-off
build leaves empty. Two builders are not like that, and the comment above them
says so: the flag-off enqueue fills one slot and the flag-off dequeue fills
four, so neither renders from an empty object. In the dequeue some slots open
Lua blocks that the shared text below them closes, which means a slot's block
depth is part of its contract and neither build renders valid Lua on its own.
That is the price of sharing 120-odd lines of a script whose two builds really
do diverge; a later commit adds a SCRIPT LOAD test so an unbalanced render
fails in CI rather than at the first EVAL.

Both builds of all seven pairs render byte-identical to the scripts they
replace, checked against the commits before this refactor rather than by
reading. Flag-off is unchanged, which is the property the dark launch rests on.

Author: 1stvamp