Bug Fix: Fixed recent regression that resulted in a false positive error related to argument-to-parameter matching.

Enhancement: Added a missing check for class-scoped covariant or contravariant TypeVars that are used in a base class where the base class defines the corresponding type parameter to be invariant. This leads to a typing hole, so it should be considered an error.

Bug Fix: Fixed a bug that led to the incorrect inferred type for a parameter in an unannotated __init__ method in the case where the method overrides a method in a base class.