We now track the variance of each typevar, and obey the `covariant` and `contravariant` parameters to the legacy `TypeVar` constructor. We still don't yet infer variance for PEP-695 typevars or for the `infer_variance` legacy constructor parameter. --------- Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com> Co-authored-by: Carl Meyer <carl@astral.sh>