Select a region for the regional recovery "bulkhead"

As discussed in the DR blueprint we will want to select a suitable region to start building out infrastructure that will be used in the unlikely scenario of a regional outage or recovery.

We should take the following into account:

1. capacity (ensuring that compute capacity can handle a full Gitaly recovery)
2. latency (we may want to have warm db replica(s) in this region, but we will also want to minimize replication lag)
3. isolation

Tasks

• Take a full inventory of compute resources required for production
• Open up a support ticket with GCP to discuss recommendations for region selection
• Finalize region selection with the working group

Note: The work here maps to key result https://gitlab.com/gitlab-com/gitlab-OKRs/-/work_items/5713+