Symfony version(s) affected: >=5.0

Description
Moving the transports to separate packages in #35422 broke BC for the stamps.

How to reproduce
Using the deprecated classes to fetch stamps does not work anymore since the stamps are now added to the envelope using the new classes. So this code $envelope->last(\Symfony\Component\Messenger\Transport\AmqpExt\AmqpReceivedStamp::class); does not find the stamp anymore.

Possible Solution
Duplicate the stamps in the evelope with the new class and deprecated classes. Or add some logic in the retrieving methods to know about new and old class names.