…r event dispatcher 5.3 (as part of Symfony 5.3)

Support Symfony 5.3

Adding changelog

This is the only way to test with PHP 8.x and Symfony 5.

symfony/symfony#41672 is blocking to update
the behat test suite. This is why I decided to add this patch. It should
not have any specific impact but for the dev environment.

After the issue has been closed on Symfony side, this commit has been
edited and is now a simple line 🎉

This commit also fixes some CS issues.
Please notice that this configuration is coming from the setono feed
bundle.

This commit fixes the following problems:
1. The script inside composer.json was failing because on Github Action
   it runs with SH and not BASH (fixed by making it external)
2. Since we run Symfony 5.x, we need to adapt the psalm configuration of
   the Symfony plugin.

Fixing test suite