Migrate pysec importer to aboutcode pipeline

[keshav-space]

[pombredanne]

Thanks for completing this!
Can you explain with a few words how to use this new pipeline?

[keshav-space]

Completed in #1628

The simple way to test this is to follow the below steps after installing VulnerableCode (https://github.com/aboutcode-org/vulnerablecode?tab=readme-ov-file#getting-started):

• Run this command to collect the pysec advisories using the new pipeline:

  python manage.py import pysec_importer