Show related issues on pipeline security tab

The activity column in the vulnerability_list.vue component can show related issues if the issueLinks are fetched. This is already done for vulnerabilities, but not yet for findings when the feature flag pipeline_security_dashboard_graphql is enabled. By showing these in the activity column, we get feature parity with the previous table component which showed the issue links below the finding title.

Before	After

Implementation steps

1. Add issueLinks in pipeline_findings.query.graphql
2. Update specs accordingly

Verification steps

1. Go to https://gitlab.com/gitlab-org/govern/threat-insights-demos/verification-projects/security-reports-pipeline-security-listing-migration-and-enhancements/-/pipelines/1100011493/security
2. Verify that the first finding has a related issue. Hover over the issue badge in the activity column. Verify it shows a popover with a link to the related issue.