[10.x] Fix parallel testing without any database connection

[deleugpn]

When running Parallel Testing, one of the checks that happens within the framework is whether we're using SQLite or not. However, this check is done via DB::getConfig(). What truly happens here is:

• DB Facade is invoked
• DatabaseManager class is resolved
• DatabaseManager::__call() is invoked
• DatabaseManager::connection() is invoked
• The default Database configuration is loaded from database.default.
• A new connection is established on this database.
• A verification of whether getConfig() returns :memory: is performed.

As we can see, even if we specify without-databases, the ParallelTesting class is still establishing a database connection.

The added test goes to show that if we create a Laravel Application and delete the database.default configuration in our project skeleton, then php artisan test --parallel --without-databases will still crash because it cannot establish a database connection to check if it's SQLite or not.

The code change partially mitigates the problem. I think a deeper issue is the fact that a complete database connection is being established just to check whether the developer is using SQLite or not. However, for the sake of simplicity and brevity, we can at least use the without-databases flag to decide to not even try connecting to any database.

[deleugpn]

I'm not sure what's going on with GitHub Actions here. I tried installing PHP 8.1 and running the tests, but they are working fine