Simplify the MySQL-on-SQLite driver API

[JanJakes]

Summary

• Remove the deprecated WP_SQLite_Driver compatibility wrapper.
• Use the PDO-compatible driver directly in the WordPress integration and MySQL proxy.
• Rename WP_PDO_MySQL_On_SQLite to WP_MySQL_On_SQLite and align implementation, test, tooling, and CI references.
• Adapt legacy SQL behavior tests and production consumers to the PDOStatement query API.

Motivation

The temporary wrapper maintained a second constructor and result API around the PDO-compatible driver. Removing it leaves one implementation and one public entry point, reducing duplicated behavior and making the API easier to understand.

Developer impact

This is a breaking public API change. Consumers using WP_SQLite_Driver must construct WP_MySQL_On_SQLite with its DSN and options, and consume query() results as PDOStatement objects. Consumers using WP_PDO_MySQL_On_SQLite must update the class name to WP_MySQL_On_SQLite.

The root wp-pdo-mysql-on-sqlite.php compatibility loader remains available; only the loaded driver class is renamed.

Testing

• composer run check-cs
• cd packages/mysql-on-sqlite && composer run test — 740 tests, 1,428,284 assertions; 15 skipped and 2 incomplete
• cd packages/mysql-proxy && composer run test — 10 tests, 20 assertions; 1 skipped