feat: add support for symfony 8

[Litarnus]

We need to cleanup composer.json and the CI config once Symfony 8 is properly released to use the stable version instead of BETA before merging this.

[garak]

Last week sentry-php released a new version compatible with Symfony 8. You should try re-running the CI

[Litarnus]

@garak I pinned the version to 4.18 now. And while the entire pipeline doesn't pass because of php-cs-fixer, Symfony 8 passes.

[garak]

@garak I pinned the version to 4.18 now. And while the entire pipeline doesn't pass because of php-cs-fixer, Symfony 8 passes.

And why did you pin it?

[Litarnus]

And why did you pin it?

My mistake, I wanted to say bumped