Add test for ccl_kernel_enqueue_native() function

- Test working with Intel and AMD CPU OCL implementations on
Linux.
- Test checks if device has CL_EXEC_NATIVE_KERNEL execution
capability, so it doesn't fail with unsupported devices such as
GPUs.
- Test will not work with OCL stub because clEnqueueNativeKernel()
is not yet implemented in the OCL stub.