Use MailPit instead of MailHog as drop-in replacement

As drop-in replacement for mailhog https://github.com/axllent/mailpit

MailPit also supports better handling of attachments

Current MailHog build https://github.com/magento/magento-cloud-docker/blob/df20834690e40b7be21eff20da3074ef409c190c/images/php/8.3-fpm/Dockerfile#L5C34-L5C71 isn't maintained regularly, last update was in 2016 https://github.com/mailhog/mhsendmail/releases/tag/v0.2.0

It's proven by Lavarel ecosystem and recommended in Laravel docs: https://laravel.com/docs/11.x/mail#mailtrap

Start with images/php/8.3-fpm/Dockerfile at the referenced MailHog build line, then inspect related image or service configuration for other MailHog references. Confirm how MailPit provides the replacement and verify that the Docker image builds and the mail service still works with the existing setup.

Written by the indexing model from the issue text.