This plumbs through the new Output method signature that accepts a table
of function pointers to values and relies on the previous storing of the
function pointers to be used for the lookup right now. This has the
elegant side-effect that Output generation could run in parallel with
the graph engine, as the engine only needs to pause to take a snapshot
of the current values tables.
Co-authored-by: Samuel Gélineau <gelisam@gmail.com>