Column accessors not available when dataframe ghost type is nested

For example:
```kt
class Holder<T>(val value: T)

private fun getMyDf() /*: Holder<DataFrame<Invoke_93>> */ = Holder(dataFrameOf("a", "b")(1, "test"))

fun main() {
    getMyDf().value.a // UNRESOLVED REF
}
```

it only works if the ghost type is top-level: 
```kt
private fun getMyDf() /*: DataFrame<Invoke_93> */ = dataFrameOf("a", "b")(1, "test")

fun main() {
    getMyDf().a // works
}
```