[BUG] cudf::test::print seg faults on nested structs

[vyasr]

Describe the bug
When used to print out nested structs, the cudf::test::print utility triggers a segmentation fault rather than printing in some cases.

Steps/Code to reproduce bug
Add these two lines:

    cudf::test::print(output, std::cerr);                                                                                                                                                                  
    //cudf::test::print(expected_structs, std::cerr);        

just before this assertion in the NestedStruct_Sliced test. The result should be fine, until the second line is commented out. Then the code will seg fault.

Expected behavior
No seg fault

[ttnghia]

This is not a bug, but rather a feature 😛

At this line, the content of expected_structs is taken over, moved into expected_struct_structs. As such, printing it will crash and this is expected.

[davidwendt]

I think that taking ownership of the parameters in this case is unexpected and the constructor should be copying the wrapper data instead of moving it.

  auto expected_struct_structs =
    cudf::test::structs_column_wrapper{{expected_structs}, cudf::test::iterators::null_at(2)};
// expected_structs is now empty/destroyed

Created PR #13243 to fix this.
The will make the corresponding constructors in structs_column_wrapper consistent with lists_column_wrapper which makes a copy of it's parameters in similar constructors.