Remove the "ci" prefix from "server_fqdn"

discussion: !146797 (comment 1805899306)

TODO:

• convert from gitlab_ci.server_fqdn to gitlab.server_fqdn
• convert from build_ci_server_fqdn to build_server_fqdn
• convert from Settings.gitlab_ci['server_fqdn'] to Settings.gitlab['server_fqdn']