This change also starts passing in the manifest interface, rather than the raw data, to the model for writing.
Note that this change does *not* backfill the existing rows in to the new tables; that will occur in a followup PR. The new columns in `tagmanifest` and `tagmanifestlabel` will be used to track the backfill, as it will occur in a worker.
Instead of 41 queries now for the simple manifest, we are down to 14.
The biggest changes:
- Only synthesize the V1 image rows if we haven't already found them in the database
- Thread the repository object through to the other model method calls, and use it instead of loading again and again
