fix(email): Emails are not sent in multiple cases

- fix(email): transactional emails are all not sent if `Use system wide (transactional) email settings` is disabled and no other email provide is setup on the Notifications page
- fix(email): no emails are sent if SMTP username and SMTP password are empty (which is the case in dev for example)
- fix(email): Wrong test email notification is used, causing the transactional email test notification to fail if no email provider is set up on the Notifications page.

app/Notifications/TransactionalEmails/Test.php

@@ -8,9 +8,10 @@ use Illuminate\Notifications\Messages\MailMessage;
 
 class Test extends CustomEmailNotification
 {
-    public function __construct(public string $emails)
+    public function __construct(public string $emails, public string $isTransactionalEmail)
     {
         $this->onQueue('high');
+        $this->isTransactionalEmail = true;
     }
 
     public function via(): array