chore: support Symfony 8 on branch 2.x

[maelanleborgne]

This pull request updates the Symfony dependencies to support Symfony 8.0 and expands the CI matrix to test against new Symfony versions. These changes ensure compatibility with the latest Symfony releases and improve test coverage.

Dependency updates:

• Updated the required versions of symfony/browser-kit, symfony/css-selector, symfony/dom-crawler, and symfony/framework-bundle in composer.json to include support for Symfony 8.0.
• Updated the required versions of symfony/phpunit-bridge and symfony/security-bundle in composer.json to include support for Symfony 8.0.

CI configuration:

• Expanded the Symfony versions in the GitHub Actions workflow matrix in .github/workflows/ci.yml to test against Symfony 7.4.* and 8.0.* in addition to the existing versions.

[kbond]

Thanks! I've upmerged 1.x into 2.x which captured this.