[3.9] gh-80254: Disallow recursive usage of cursors in `sqlite3` converters (#92278)

* [3.9] gh-80254: Disallow recursive usage of cursors in `sqlite3` converters

(cherry picked from commit c908dc5b4798c311981bd7e1f7d92fb623ee448b)

Co-authored-by: Sergey Fedoseev <fedoseev.sergey@gmail.com>
Co-authored-by: Jelle Zijlstra <jelle.zijlstra@gmail.com>

* Fix ref leak in pysqlite_cursor_iternext

* Explicitly free resources at test tearDown()