Extend gitlab-qa Airgapped tests to run against GitalyCluster

Overview

Currently the airgapped scenario only runs against a single Gitlab node. We would like these airgapped tests to be run against Gitaly Cluster node while Gitaly and Praefect networks are completely isolated.

Approach

As a first iteration - we will work towards only running against the smaller subset of smoke tests with Run airgapped smoke tests on gitaly cluster (!1098 - merged)

As a follow up we will extend to run against a broader suite of tests Extend airgap to use gitaly cluster for a broad... (!1092 - merged) and reintroduce the use of iptables on the Gitlab instance to restrict network access and give the ability to access registry.gitlab.com to download runner images for tests that make use of runners.

We're planning to have all E2E tests initially running in the nightly jobs, except for a small subset that are flagged as gitlab and skip_live_environment. Once that is proven stable, we can consider moving it into further pipelines.

Tasks

Edited by John McDonnell