Re: Zero copy cast kernels

[Rok Mihevc]

For scalar casting tests we use CheckCastZeroCopy [1] which you could reuse.

[1]
https://github.com/apache/arrow/blob/e7d6c13d4ae3d8df0e9b668468b990f35c8a9556/cpp/src/arrow/compute/kernels/scalar_cast_test.cc#L128-L138

Rok