refactor(run-engine): share one copy of the ck ack, nack and dead-letter lua

Each virtual-time command was a copy of its non-vtime counterpart with a few
lines added, which meant a change to one of the originals did not reach its
copy. That has already cost us twice: the TTL re-registration main added, and
the snapshotRoute read it added before that.

Each of these three scripts is now written once, with named slots the
virtual-time build fills and the flag-off build leaves empty. Rendering the
flag-off build with no slots reproduces the previous script byte for byte,
which is the property the dark launch rests on, and is checkable by hashing
rather than by reading. There is no second copy left to drift.

The slots are insertion points only and the shared text keeps its original
order and formatting, so a rewrite of one of these scripts upstream still
merges around them.

No behaviour change: both renders are byte-identical to the scripts they
replace.

Author: 1stvamp