Sync Vulnerabilities ES index for model callbacks and pipeline bulk ingestion

As mentioned in the documentation, before the backfill of Vulnerabilities index, we have to perform continous updates behind a FF and fully enable the FF before the backfill.

Continous updates involves:

1. Active Record model callback
2. Bulk creation/updation of vulnerabilities done in the ingestion framework outside Active Record.

Note that deletion and transfer sync is tracked in #535117 (closed)