[6.x] Add serializable classes to allowlist

[duncanmcclean]

Laravel recently introduced the serializable_classes config to limit which classes with __destruct, __wakeup methods can be deserialised.

This option is false in new Laravel 13 applications, meaning you'll see an error when Statamic attempts to retrieve objects from the cache:

The script tried to call a method on an incomplete object. Please ensure that the class definition "Illuminate\Support\Collection" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide an autoloader to load the class definition

This PR fixes it by adding specific classes from Statamic to the allowlist, preventing the error.

Related: laravel/framework#58911