Ceo Shadow related MRs

Anything related to `.gitlab-ci.yml` or pipelines. Owner: Engineering Productivity team.

Issues that have been identified as a blocker to the epic: Sharding - Database Scalability - &5759

Issues that are not blocking the rollout of decomposition into production.

Blocks a phase of &6160 - Deploy a Patroni Cluster

Blocks a phase of &6160 - Configure Patroni standby cluster

Blocks a phase of &6160 - Serve CI reads from CI standby cluster

Blocks a phase of &6160 - Separate write connections for CI and Main (still going to the same primary host)

Blocks a phase of &6160 - CI migration downtime

Blocks a phase of &6160 - Validation

Blocks a phase of &6160 - Promotion of CI database

Issues related to the CI components

Issues for milestone planning and weighting/research in preparation for milestone planning