[Python][Java][Docs] Update the "Integrating PyArrow with Java" documentation section to not use `_import_from_c`/`_export_to_c`

Currently, the "Integrating PyArrow with Java" page (https://arrow.apache.org/docs/13.0/python/integration/python_java.html) has an example that uses the low-level `_import_from_c` / `_export_to_c`. We should see if we can update this guide to not use those methods directly.

Probably, this is blocked (or would be solved) by re-implementing the `pyarrow.jvm` module to use the C Data Interface:

* https://github.com/apache/arrow/issues/44860