Remove records from `security_findings` where UUID is null

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.

In #277327 (closed) we have fixed all records for which we could compute the UUID. The remaining records are unsalvageable due to expired build artifacts or missing primary identifiers.

Implementation plan

• database Write a background migration to drop records from security_findings table where uuid column is null