Symfony version(s) affected: symfony/messenger: ^5

Description
Currently the symfony/messenger has no dependency in composer.json to symfony/event-dispatcher, but the Code internally relies on Symfony\Component\EventDispatcher\LegacyEventDispatcherProxy and is not replaceable by e.G. just using the event-dispatcher-contracts as dependency.

See:

• Symfony\Component\Messenger\Worker - https://github.com/symfony/messenger/blob/39444584eaec8a351da331e519d705931aa97235/Worker.php#L50
• Symfony\Component\Messenger\Middleware\SendMessageMiddleware - https://github.com/symfony/messenger/blob/5c2a1563ad7cae9f4b51a7d968f179a576ae840e/Middleware/SendMessageMiddleware.php#L38

How to reproduce
Send a Message asynchronously without having symfony/event-dispatcher as dependency. 💥

Possible Solution

v1: Add symfony/event-dispatcher as require in composer.json

v2 (prefered): Use the injected Symfony\Contracts\EventDispatcher\EventDispatcherInterface correctly without relying on the LegacyEventDispatcherProxy-class to be there.