[BUG] Without providing metadata cannot round-trip struct columns via interop/from/to_arrow

**Describe the bug**

```python
import pyarrow as pa
import pylibcudf as plc

host_c = pa.array([{"a": [1, 2], "b": [3, 4]}])
device_c = plc.interop.from_arrow(host_c)
on_host = plc.interop.to_arrow(device_c)

# > RuntimeError: CUDF failure at: /home/coder/cudf/cpp/src/interop/to_arrow_schema.cpp:146: Number of field names and number of children doesn't match
```

We either need to construct appropriate (empty) metadata for child columns, or handle it in to_arrow_schema on the C++ side.