Recover gracefully from laptop sleep

[enocom]

Right now if a laptop goes to sleep with an active connection to a Cloud SQL instance, the socket factory won't recover on its own once the laptop has been restored.

There are limitations in Java to handling this:

https://stackoverflow.com/questions/52876556/how-does-java-calculate-sleep-time-when-pc-goes-into-hibernate-mode

Nonetheless, we should throw out a bad connection and force a refresh, such that the socket factory recovers gracefully from sleep.

See https://github.com/luryus/cloud-sql-jdbc-hang for a reproduction of this issue.

Related to GoogleCloudPlatform/cloud-sql-proxy#1788.

Whatever we do here, we should port to the AlloyDB Java Connector as well.

[enocom]

cc @luryus

This is a problem across Connectors and we do want to improve support for sleep.