FieldKind.of logic is wrong for FrameColumn/ColumnGroup

[koperagen]

For example expected type of a is DataColumn<DataFrame<LocalType>?>, but schema - FrameColumn.

val df = dataFrameOf("a" to columnOf(List(4) {
    dataFrameOf(
        "c" to columnOf(2)
    )
}))

val res = df.convert { a }.with { it.takeIf { it.rowsCount() % 2 == 0 } }
res[0].a?.c


// FieldKind.of is wrong =(
println(res.compileTimeSchema())

For now this logic is used in toDataFrame (library), compileTimeSchema (library), and extract schema from DataSchema declarations (compiler plugin, maybe in Jupyter integration)

Potential problems:

1. Incorrect compileTimeSchema
2. Extension properties for res are correct, but after another operation plugin will perform extract schema and probably some kind of runtime exception could happen while accessing a/c in df1
   val df1 = res.add("addMe") { 123 }

[zaleslaw]

@koperagen are you going to fix during next 1-3 weeks?