This commit doesn't change behaviour of any inference algorithm, it
introduces opportunity to switch constraint system that is used for
overload resolution and fix problematic cases by changing one enum
entry.
Due to fundamental changes, there are cases where a new inference
algorithm reports overload resolution ambiguity errors (#KT-31670,
#KT-31758), which is correct from its point of view. However, this is
a breaking change and to really make it, we should be very confident
and have enough motivation for it, therefore, we don't change behavior
now in order to collect more examples (if there are any). And if we
find a lot of erroneous examples, we'll be able to change the behavior
quite simply
Mikhail Zarechenskiy