Laravel components v8 (#2576)

- update actions ci
- include json for 4 spaces tab
- provide output int for process code exit
- adhere to parent type hint of builder
- mailer instance now needs a name, multiple can be instantiated
- getOriginal now uses mutators in the model
- Temporarily loosen MailableInterface requirements. This avoids an immediate BC break for classes in extensions that implement this interface.
- Temporarily provide (and autoload) old symfony translator interface
- make queue exception handler compatible with the contract of L8
- Update phpunit schema for newer version
- Update phpunit assert calls for newer version

src/Locale/LocaleServiceProvider.php

@@ -15,7 +15,8 @@ use Flarum\Foundation\Paths;
 use Flarum\Settings\SettingsRepositoryInterface;
 use Illuminate\Contracts\Events\Dispatcher;
 use Illuminate\Contracts\Translation\Translator as TranslatorContract;
-use Symfony\Component\Translation\TranslatorInterface;
+use Symfony\Component\Translation\TranslatorInterface as DeprecatedTranslatorInterface;
+use Symfony\Contracts\Translation\TranslatorInterface;
 
 class LocaleServiceProvider extends AbstractServiceProvider
 {
@@ -62,9 +63,11 @@ class LocaleServiceProvider extends AbstractServiceProvider
 
             return $translator;
         });
+
         $this->container->alias('translator', Translator::class);
         $this->container->alias('translator', TranslatorContract::class);
         $this->container->alias('translator', TranslatorInterface::class);
+        $this->container->alias('translator', DeprecatedTranslatorInterface::class);
     }
 
     private function getDefaultLocale(): string