Type inference of `Array<primitive>` may be unpredictable

[Jolanrensen]

From:
https://youtrack.jetbrains.com/issue/KT-52170/Reflection-typeOfArrayLong-gives-classifier-LongArray

In DataFrame we rely a lot on reflection and typeOf<>(), however, a thing to note is that typeOf<Array<Int>>().classifier == IntArray::class instead of Array::class as might be expected.

This might cause unexpected bugs, so refer to this issue when we find one.