Add vulnerability in PipelineSecurityReportFinding

What does this MR do and why?

This MR adds the vulnerability field to the PipelineSecurityReportFinding GraphQL type.

Screenshots or screen recordings

How to set up and validate locally

1. Run a pipeline on a main branch of a project with vulnerabilities
   • Sample project
2. Run the following GraphQL query. You should see the vulnerability data

{
  project(fullPath: "<project_path>") {
    pipeline(iid: "1") {
      id
      securityReportFindings {
        nodes {
          title
          uuid
          vulnerability {
            description
          }
        }
      }
    }
  }
}

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #340558 (closed)