[Form][2.8,3.0] Type guesser guesses alias instead of FQCN

[hiddewie]

In the file Symfony/Bridge/Doctrine/Form/DoctrineOrmTypeGuesser.php of branch 2.8 (and master), the quessed form types are the old aliases. They should be updated to quess the FQDN of the form type, as decided and implemented in #15079.

[Tobion]

Yeah I also saw that when working on #16302

[hiddewie]

After my PR has been merged and 2.8 has been merged into master, I'll create a new pull request with the same edits using the ::class constant.