CP-17204 connection lost

[niden]

Hello!

• Type: new feature
• Link to issue: [NFR]: Add a way to verify/ensure the database connection is open in AbstractPdo #17204

In raising this pull request, I confirm the following:

• I have read and understood the Contributing Guidelines
• I have checked that another pull request for this purpose does not exist
• I wrote some tests for this PR
• I have updated the relevant CHANGELOG
• I have created a PR for the documentation about this change

Added connection-liveness and opt-in auto-reconnect support to Phalcon\Db\Adapter\Pdo\AbstractPdo: ping() (a SELECT 1 probe), ensureConnection() (reconnect in place when the probe fails), and setAutoReconnect()/getAutoReconnect() (also settable via the autoReconnect descriptor key). When auto-reconnect is enabled and a query fails on a lost ("gone away") connection outside a transaction, execute() and query() fire the new db:connectionLost event, reconnect, and retry the statement once; a loss inside a transaction is re-thrown without retry. "Gone away" detection is provided per driver by Phalcon\Db\Adapter\Pdo\Mysql (error codes 2006/2013) and Phalcon\Db\Adapter\Pdo\Postgresql (SQLSTATE 08003/08006/57P01-03), with a message fallback.

Added the same liveness and opt-in auto-reconnect support to Phalcon\DataMapper\Pdo\Connection (ping(), ensureConnection(), setAutoReconnect()/getAutoReconnect()), wrapping exec(), perform(), prepare(), and query() with the single-retry behavior. This connection has no events manager, so no db:connectionLost event is fired; "gone away" detection is driver-agnostic and the in-transaction guard uses a locally tracked transaction level.

Thanks