#PHPUnit 10

We need to convert all tests from annotation to attributes, first.

I'm afraid we have to reopen this is light of PHPUnit 12 - that is making final the constructor of TestCase. We can no longer override it to set programmatically at the base class level.

The issue was reported upstream but no alternatives were suggested: https://github.com/issues/created?issue=sebastianbergmann%7Cphpunit%7C5838

So I think we need to

• add the #[RunTestsInSeparateProcesses] attribute to all existing kernel and functional tests
• add a PHPStan rule that will prevent new kernel and functional tests to miss the attribute