Migrate dev.gitlab.org from Azure to GCP

Summary

dev.gitlab.org is a crucial to our delivery process as we pull our Docker images from it. Since we're deployed in GCP, pulling from an Azure machine (that is, dev.gitlab.org) is non-intuitive and can make it hard to debug networking issues between the two cloud providers.

Also dev is configured as a SSO for Sentry, which is important for developers and SREs alike.

As a result of our dependency on the machine, we can't afford to have it down for a long period of time (hours or days), hence we need to carefully plan on how to migrate it to GCP while preserving its state (PostgreSQL, ...).

In a way, this migration could be similar to migrating Chef from Digital Ocean to GCP, so &138 (closed) could be used a blueprint/guideline.

Related Incident(s)

Originating issue(s):

• production#6065 (closed)
• https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/6083

Desired Outcome/Acceptance criteria

The desired outcome is dev.gitlab.org would be served from GCP.

Associated Services

Corrective Action Issue Checklist

• link the incident(s) this corrective action arose out of
• give context for what problem this corrective action is trying to prevent from re-occurring
• assign a severity label (this is the highest sev of related incidents, defaults to 'severity::4')
• assign a priority (this will default to 'priority::4')