Follow-up from "Geo: Constantly reverify repositories"

The following discussion from !8550 (merged) should be addressed:

• @stanhu started a discussion:

  This can go in a separate issue, but I wonder how we can evaluate whether reverification is helping by logging when a repository has been detected as inconsistent.

  I think we'll also want to have Prometheus metrics for how frequently we're selecting projects to reverify versus the normal verification.