Zend: Implement __unserialize() for Exception/Error

[Girgias]

This makes the DOM classes the only classes that only have __sleep() magic methods, and __wakeup() methods without a corresponding __unserialize() magic method, as it is needed to allow serialization of child classes.

[Girgias]

I am closing this as the reason for __wakeup() to exist is to verify the type of the message and code properties. As those would, hopefully, use actual property types in PHP 9 we can then just remove the __wakeup() method as it will then serve no purpose.