Send COM_RESET_CONNECTION in mysqlnd_conn_data::restart_psession

[TimWolla]

Description

Inspired by the mailing list thread at https://externals.io/message/128741.

To make the use of persistent connections with MySQL somewhat safer, MySQLnd should send a connection reset when “restarting” a persistent session.

According to https://dev.mysql.com/doc/c-api/8.4/en/mysql-reset-connection.html, MySQL should then take care of cleaning up all connection-specific state.

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restart_psession is invoked here in pdo_mysql_handle_factory. However that is skipped when re-using a persistent connection. Indeed if I set a breakpoint on restart_psession, it's only invoked on the first request. So I feel like I'm missing something...