This cuts varcon lookup times in half but I still suspect slower than
phf. Like with bsearch and unlike, the cost is consistent between hits
and misses.
At least this doesn't have the compile hit of PHF + unicase. Maybe I
should experiment with integrating a non-const-fn variant of unicase
with PHF and give up on all of this extra complexity.
Before, only some dicts did we guarentee were pre-sorted. Now, all are
for-sure pre-sorted.
This also gives each dict the size-check to avoid lookup.
But this is really about refactoring in prep for playing with other
lookup options, like tries.
