Geo: Add models to prepare for project repo replication v2

What does this MR do and why?

This code change adds support a new verification system for project repositories in GitLab's Geo feature.

It adds the models ProjectRepository and ProjectRepositoryState in the EE module and factories and tests for them.

References

Geo: Enumerate project_repositories instead of ... (#546175)

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Before	After

How to set up and validate locally

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