Expand PDO API coverage

[JanJakes]

Summary

Stacked on #469.

This expands PDO compatibility for WP_MySQL_On_SQLite before 3.0 by covering connection diagnostics, constructor options, result statements, column metadata, and PHP 8.4's connection factory. Prepared statements now fail through standard PDO diagnostics until parameter binding can be implemented safely across the full translation pipeline.

• Implement lastInsertId(), errorCode(), and errorInfo() without relying on uninitialized parent PDO state.
• Isolate the public last insert ID from internal information-schema writes.
• Honor numeric PDO constructor options, including fetch, stringification, persistence, and error modes, while keeping internal SQLite operations exception-safe.
• Initialize PDOStatement::$queryString and delegate safe result-statement methods including iteration, closeCursor(), bindColumn(), nextRowset(), diagnostics, and debugDumpParams().
• Snapshot result column metadata into each statement, implement getColumnMeta() with its array|false contract, and migrate the WordPress and MySQL proxy consumers.
• Deprecate the stateful get_last_column_count() and get_last_column_meta() compatibility methods.
• Populate PDOException::$errorInfo with native SQLite or emulated MySQL diagnostics.
• Override PDO::connect() on PHP 8.4+ so it creates the emulated connection.
• Report prepare() as unsupported with SQLSTATE IM001, respecting the configured PDO error mode instead of triggering an uninitialized-object error.

[JanJakes]

Searches: Veloria, GitHub.

The only external consumer is Automattic/markdown-database-integration, which we can help handle. The deprecated WP_SQLite_Driver facade retains get_insert_id() for legacy consumers.

[JanJakes]

Searches: Veloria, GitHub.

No external consumers call these methods directly on WP_MySQL_On_SQLite. The deprecated WP_SQLite_Driver facade retains them, while PDO consumers use PDOStatement::columnCount() and PDOStatement::getColumnMeta().