This does not yet yield the produces ASG, but does set up the lowering
pipeline to prepare to produce it. It's also currently a no-op, with
`NirToAsg` just yielding `Incomplete`.
The goal is to begin to move toward vertical slices for TAMER as I start to
return to the previous approach of a handoff with the old compiler. Now
that I've gained clarity from my previous failed approach (which I
documented in previous commits), I feel that this is the best way forward
that will allow me to incrementally introduce more fine-grained performance
improvements, at the cost of some throwaway work as this progresses. But
the cost of delay with these build times is far greater.
DEV-13429
Mike Gerwitz