Set vulnerability_occurrence_id on vulnerability_reads during ingestion

What does this MR do and why?

As part of the vulnerabilites on multiple branches project, we are changing vulnerability_reads so that they are related to a vulnerability_occurrence rather than a vulnerability. This change sets the vulnerability_occurrence_id during ingestion so that the relationship is tracked for new records.

References

Relates to: #555981 (closed)

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Before	After

How to set up and validate locally

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