VCIO-next: Advisory model migration Batch 2

[TG1999]

• postgresql
• elixir security
• Xen
• Curl
• Istio
• OSSFuzz
• Mozilla

[TG1999]

This is done now!

PRs for references:
#1946

To test this:
Set up Vulnerablecode on your system locally and run a new V2 importer pipeline for example:

./manage.py import --l

You will be able to see

postgresql_importer_v2
xen_importer_v2
oss_fuzz_importer_v2
mozilla_importer_v2
istio_importer_v2
curl_importer_v2
elixir_security_importer_v2

All of these importers are migrated to V2 and are ready to import Advisory level info