Add `deprecate_vulnerability_occurrence_pipelines` FF to pipelines

What does this MR do and why?

This MR is part of the epic Delete `vulnerability_occurrence_pipelines` table (&11241)

The EE::Ci::Pipeline model has a vulnerability_findings association that currently goes through: :vulnerabilities_finding_pipelines

This association is used to fetch all of the vulnerabilities associated with a pipeline in:

• ee/app/services/sbom/ingestion/vulnerabilities.rb#L49-55
• ee/lib/gitlab/ci/parsers/security/dependency_list.rb#L35

This MR allows us to be able to toggle between the existing implementation, which goes through: :vulnerabilities_finding_pipelines, and the new implementation, which will use finding.latest_pipeline_id and finding.initial_pipeline_id, with the deprecate_vulnerability_occurrence_pipelines feature flag

MR acceptance checklist

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resolves #450943 (closed)
Related to #422384 (closed)