Avoid breaking existing code with Iterable<DataSchema>.toDataFrame() calls when enabling the plugin

Problem from example being converted to use plugin found by @Jolanrensen
```kt
@DataSchema
data class MySchema(val i: Int)

fun main() {
val df: DataFrame = listOf(MySchema(1)).toDataFrame() // breaks when plugin is enabled, type is now MySchema_98

df.toList() // breaks when plugin is enabled
}
```

Proposed change:
Add toDataFrame overload. If T is already DataSchema type, no need to introduce plugin-generated local type.
```kt
public inline fun Iterable.toDataFrame(): DataFrame =
@DisableInterpretation toDataFrame {
properties()
}
```