Modify mail_room to crash with json

This MR updates the mail_room gem usage to include --log-exit-as parameter. This allows crash logs to be written as a single JSON object rather than multiple lines for easier intake into ElasticSearch.

See:

Original PR: https://gitlab.com/gitlab-org/gitlab-mail_room/-/blob/master/lib/mail_room/cli.rb#L28-30

@cmiskell's original comment

All structured makes our log ingestion (to ElasticSearch) a lot more reliable/better. I can't find the link right now, but I think sidekiq is causing us problems (particularly running in k8s) where some logs are JSON structured and some are not. So I'd prefer exclusively structured.

Original issue: gitlab#30070 (closed)

mail_room fork issue: gitlab#207207 (closed)

MR (mail_room upgrade): gitlab!25869 (merged)

CNG MR (mail_room upgrade): gitlab-org/build/CNG!393 (merged)

CNG MR (use --log-exit-as): gitlab-org/build/CNG!395 (merged)