Test Gitaly Cluster and Praefect to evaluate adding to Reference Architectures

Gitaly Cluster (and Praefect) are close to GA and as such the Reference Architectures need to be updated and tested along with Docs updated.

As part of the performance tests we should also do these workflow tests - https://gitlab.com/gitlab-org/quality/team-tasks/-/issues/451#ha-workflow-tests.