Two things at ones, as there was no clean way to seperate the commit and
give me feedback from the tests.
But the model Artifact is now JobArtifact, and the table does not have a
type anymore, but the metadata is now its own model:
Ci::JobArtifactMetadata.
This adds counters for build artifacts and LFS objects, and moves
the preexisting repository_size and commit_count from the projects
table into a new project_statistics table.
The counters are displayed in the administration area for projects
and groups, and also available through the API for admins (on */all)
and normal users (on */owned)
The statistics are updated through ProjectCacheWorker, which can now
do more granular updates with the new :statistics argument.
