Store group and project full name and full path in routes table

What does this MR do?

• adds name field to routes table
• moves full_name and full_path implementation from Namespace/Project to Routable concern
• uses route.name and route.path for full name/path to group or project

Are there points in the code the reviewer needs to double check?

no

Why was this MR needed?

• less sql queries (no need to collect parents to build full name/path)
• use routes table as single point of truth for resource location
• cleaner code

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/2772