Fix: Removing the "ci" prefix from "server_fqdn" variable

What does this MR do and why?

This MR addresses removes the "ci" prefix from the server_fqdn variable. The change aims to standardize the naming convention of the server_fqdn variable across the codebase.

As a summary:

• 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']

Fixes #451233 (closed)