Support ActiveJob adapters with pre-deserialized events and NULL serializer

[milgner]

Depending on the configuration of the ActiveJob backend and the serializer used - i.e. the NULL serializer -, it is possible that the argument to perform is already a full Event record. In that scenario, it can be used as-is without prior processing.

Closes #1334, even if the approach is different from how I understood the problem at first glance. But when taking a closer look at Record, DeserializedRecord and the transformation pipeline I understood better the way things are related and decided on a more straightforward solution and just detecting that specific situation.