IBX-8470: Upgraded codebase to Symfony 6

[alongosz]

Caution

This is a part of bigger set of changes, to be merged together when ready

• ❗ Remove TMP commits before merge ❗

🎫 Issue	IBX-8470

Related PRs:

• IBX-8470: Upgraded codebase to Symfony 6 core#447
• IBX-8470: Bumped Symfony to version 6 doctrine-schema#27

Description:

This PR bumps Symfony to v6 with some codebase upgrades.
Additionally I saw we still use SiteAccess as a service and inject it. Replaced it with SiteAccessServiceInterface.
No test coverage, nor PHPStan to check if this works...

Key changes:

• [Git] Added missing contracts and lib directories
• [Git] Added tests directory
• Bumped Symfony packages requirements to ^6.4
• Improved code of related Symfony bundle extension points
• Dropped obsolete ezplatform:cron:run command alias
• Improved codebase quality
• Injected SiteAccessServiceInterface into CronJobsRegistry
• [Git] Updated PHP CS Fixer cache .gitignore entry

QA:

Sanities in the form of regression tests.

Documentation:

No documentation required.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud