Allow type variable fixation into intersection type if it isn't meaningless (i.e. has one or more final classes, or two or more open classes)

^KT-46186 Fixed

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/types/IrTypeSystemContext.kt

@@ -158,6 +158,10 @@ interface IrTypeSystemContext : TypeSystemContext, TypeSystemCommonSuperTypesCon
 
     override fun TypeConstructorMarker.isClassTypeConstructor() = this is IrClassSymbol
 
+    override fun TypeConstructorMarker.isInterface(): Boolean {
+        return (this as? IrClassSymbol)?.owner?.isInterface == true
+    }
+
     override fun TypeParameterMarker.getVariance() = (this as IrTypeParameterSymbol).owner.variance.convertVariance()
 
     private fun getSuperTypes(typeParameterMarker: TypeParameterMarker) = (typeParameterMarker as IrTypeParameterSymbol).owner.superTypes