Geo - Remove FDW related code

To-Do List

• !38617 (merged) - Remove Geo::RegsitryFinder#current_node_fdw method;
• !38617 (merged) - Remove Geo::Fdw::GeoNode, Geo::Fdw::GeoNodeNamespaceLink, Geo::Fdw::Namespace, and Geo::BaseFdw models;
• !38617 (merged) - Remove FDW code from Geo::SelectiveSync concern;
• !38620 (merged) - Remove FDW health checks from Gitlab::Geo::HealthCheck;
• !38632 (merged) - Remove Gitlab::Geo::GeoTasks#refresh_foreign_tables! method;
• !38632 (merged) - Remove Gitlab::Geo::GeoTasks#foreign_server_configured method;
• !38632 (merged), omnibus-gitlab!4475 (merged) - Remove rake task to refresh foreign tables definition in Geo Secondary node from ee/lib/tasks/geo.rake (changes in omnibus are required);
• !38629 (merged) - Remove SystemCheck::Geo::FdwEnabledCheck method;
• !38629 (merged) - Remove SystemCheck::Geo::FdwSchemaUpToDateCheck;
• !38629 (merged) - Remove FDW checks from SystemCheck::RakeTasks::GeoTasks class;
• !38718 (merged) - Remove Gitlab::Geo::Fdw class;
• !38718 (merged) - Refactor specs to remove the geo_fdw tag;
• !38718 (merged) - Remove the geo_fdw tag;
• !38726 (merged) - Update CI to not set up FDW;
• !38938 (merged) - Remove step to fix FDW settings for QA;