Configure Sentry containers

Summary:
Sentry requires a fair number of containers. It will be deployed like this:

• sentry_db (PostgreSQL)
• sentry_redis
• sentry_smtp (Exim)
• sentry_web_1 (Django application)
• sentry_worker_1
• sentry_cron

This change doesn't deploy anything but declare the configuration
of all those services.

Reference: https://docs.sentry.io/server/installation/docker/

Ref T1360

Test Plan: no op in production

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1360

Differential Revision: https://devcentral.nasqueron.org/D1977