bpo-16580: [doc] Add examples to int.to_bytes and int.from_bytes (GH-27760)

* added code equivs. for to_bytes and from_bytes

Based on woparry's patch[1] from the relevant issue thread[2].

[1]: https://bugs.python.org/file30372/issue16580.patch
[2]: https://bugs.python.org/issue16580

Co-authored-by: Mark Dickinson <dickinsm@gmail.com>