[Messenger] Move Transport/InMemoryTransport to Transport/InMemory/InMe…

[nicolas-grekas]

Q	A
Feature PR	symfony/symfony#48614
PR author(s)	@lyrixx
Merged in	6.3

[lyrixx]

For the record:

>…e/dev/github.com/symfony/symfony-docs(translit-emoji) rg InMemoryTransport
messenger/custom-transport.rst
129:be implemented. For real implementations see :class:`Symfony\\Component\\Messenger\\Transport\\InMemoryTransport`

messenger.rst
1519:    use Symfony\Component\Messenger\Transport\InMemoryTransport;
1530:            /* @var InMemoryTransport $transport */

[javiereguiluz]

Fixed in #17574.