Since nullability-flexible types in IR are represented by an annotation
on an IrSimpleType, not a special instance, the common implementation of
`KotlinTypeMarker.isMarkedNullable` in `TypeSystemContext` doesn't work.
This method is used for example to generate `typeOf` in JVM IR, in
`TypeSystemCommonBackendContext.generateTypeOf`, and this issue led to a
difference in behavior of `typeOf` for nullability-flexible types.
#KT-44726 Fixed
Alexander Udalov
e6476c39ca