[5.5] Clone Job specific properties

[themsaid]

Taking a Mailable for example, while queuing it a SendQueuedMailable is dispatched which holds the mailable as a $mailable property.

While the job is being serialized, if the mailable uses the SerializesModels trait all properties referencing an Eloquent Model will have its value replaced with a ModelIdentifier, taking into account that we serialize a cone of the job in Queue::createObjectPayload() one might think that the mailer object will still hold references to Model objects in the original job instance, but this is not the case since the original job and the clone both points to the same reference of the mailable, and thus the __sleep method that ran while serializing will affect the mailable in the original as well.