Delta catch up should optimize for bulk when the gap is too large

[RaitoBezarius]

Delta CVE should error if the gap is too large.

We should also create a new toplevel management command called ingest_cve which does either bulk ingestion or delta ingestion based on the situation. Old commands can be kept for more advanced users.

Bulk ingestion should probably also skip existing CVEs.

This way, our CVE ingestion process becomes quite rock-solid.