DevKit updates for 4.x branch

[SonataCI]

Changelog

### Removed
- Support for PHP 7.4
- Support for Symfony 6.0 and 6.1
- Support for `doctrine/persistence` ^2.0.

[jordisala1991]

2 errors missing from psalm, not sure how to fix them @VincentLanglet , can you help me?

[VincentLanglet]

2 errors missing from psalm, not sure how to fix them @VincentLanglet , can you help me?

Sure:

ERROR: InvalidArgument - src/CmsManager/CmsSnapshotManager.php:154:56 - Argument 1 of Sonata\BlockBundle\Util\RecursiveBlockIteratorIterator::__construct expects Doctrine\Common\Collections\Collection<array-key, mixed>|array<array-key, mixed>, but Doctrine\Common\Collections\Collection<array-key, Sonata\PageBundle\Model\PageBlockInterface> provided (see https://psalm.dev/004)
        $iterator = new RecursiveBlockIteratorIterator($page->getBlocks());

This error need to be fixed in BlockBundle by changing Collection phpdoc to ReadableCollection in order to accept covariance. (You can try with sonata-project/SonataBlockBundle#1142)

And for

$template = new Template('page', 'template.twig', ['header' => [
            'name' => 'Header',
            'block' => ['text.block'],
        ]]);

we're passing block and not blocks.