Geo: Remove legacy replication for project repositories

As a first iteration, we are introducing replication and verification through SSF for project repos behind a FF, while still keeping the old replication code working. As the next step we want to remove the legacy code and at the same time remove the FF, so that replication works through the SSF.

• Remove the legacy services and workers
• Update all the needed documentation
• Remove 'verification_failed_repos' and verification_failed_wikis scopes
• Remove legacy counters repositories_count and other
• Remove deprecated Geo Status Widget 5d467f01
• Remove Geo::ProjectHousekeepingService
• Remove project_repository_states table
• Remove deprecated controllers
• Remove deprecated views and HAML files

This is not a comprehensive list!