Geo: Insert a record in project_repositories only when a Git repo is inserted

This is part of a multi-step implementation plan to handle Geo verification/replication of projects without Git repositories to reduce errors caused when Gitaly tries to fetch non-existent repos.

	Steps
1	Add has_repo column in <repo type>_repositories table
2	Backfill has_repo column
3	Introduce a feature flag to be used in the next two steps
4	Insert record in <repo type>_repositories only when a Git repo is created; at the same time update has_repo	👈 You are here
5	Do not attempt to verify/replicate Git repo when <repo type>__repositories (and Git repo) doesn't exist
6	Enumerate <repo_type>_repositories instead of repo types table for verification/replication of Git repos, if not already done
7	Delete project_repositories rows where Git repos don't exist

We want to make sure a project_repositories record exists only if a Git repo exists, since it represents a Git repo in the rails code.

Insert a record in this table, every time a Git repo is inserted for a gitlab project and update has_repo in projects.