Populate missing `finding_uuid` values for existing `vulnerability_feedback` records

Why are we doing this work

We are in the process of deprecating the usage of the project_fingerprint attribute of the findings. By using uuid values to identify findings, we can easily associate any related entity with finding.

Implementation plan

• backend Write a background migration to populate missing finding_uuid values for the vulnerability_feedback table.
  • Entries that don't have a report available are to be deleted