Provision an environment for DB benchmarking

This covers what we'd call the "phase I" of this epic, outlined here: https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/11675#note_460851193.

Acceptance criteria

• Create environment module on env-projects: https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/12114
• Document reserved IP space: gitlab-com/runbooks!3063 (merged)
• Setup Cloud NAT and bastion for access to the environment: https://ops.gitlab.net/gitlab-com/gitlab-com-infrastructure/-/merge_requests/2253 https://ops.gitlab.net/gitlab-com/gitlab-com-infrastructure/-/merge_requests/2256
• Create required chef-repo roles: https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/12157
• Provision required VMs: https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/12158
• Create initial copy of the production database: https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/12159