Encode constraints that hold at all points as logical edges in location-sensitive polonius
Currently, with the full setup in #134980 (but is from #134268), the polonius location-sensitive analysis converts `Locations::All` typeck constraints as edges at all points in the CFG. This was temporary.
There's a FIXME about that already, and this PR implements it: we now use the constraints that hold at all points during traversal instead of eagerly materializing them as physical edges.
Another easy one `@jackh726.`
This fixes the slowness that was happening on the big CFG from the `saturating-float-casts` test (because of its 12M materialized edges) without, AFAICT, simply moving this overhead to traversal: materializing the logical edges is done on-demand.
r? `@jackh726` (no rush either)
Matthias Krüger
56447d738b