Allow Annotations 2, add attribute support to testing fixtures and test with attributes when able, allow the Annotations package to be an optional dependency

[mbabker]

This can supersede #1596

This PR will:

• Allow doctrine/annotations 2.x to be installed
• Makes the Annotations package optional by moving it to require-dev and unloading the doctrine.orm.metadata.annotation_reader service alias if not installed
• Explicitly configures whether annotation support should be enabled in test fixtures instead of relying on feature detection in the FrameworkBundle (which relies on the package existing in someone's require list)
• Adds attributes to the RepositoryServiceBundle test fixture bundle that is loaded by Doctrine\Bundle\DoctrineBundle\Tests\DependencyInjection\Fixtures\TestKernel
• Configures resources using the RepositoryServiceBundle test fixture bundle to use attributes when run on PHP 8 and annotations on PHP 7
• Skips tests if run on PHP 7 and the Annotations package isn't installed

[maxhelias]

The CI will be fixed only when symfony/symfony#48725 is released

[mbabker]

No, it's symfony/symfony#48718 that most of the CI's waiting for (there's also psalm/psalm-plugin-symfony#296 which was needed to unblock SA but that looks to be released now); that particular change removes some code from Symfony 6.3 only that was only needed to support old Annotations versions.

[maxhelias]

Yeah i missed that one 👍

[derrabus]

Thank you @mbabker!