Frontend: Use Pipeline.securityReportFinding endpoint fetch feedbacks

Summary

Use the Pipeline.securityReportFinding query to fetch the mergeRequest, issueLinks and stateComment fields.

Why

These are replacing the legacy issue_feedback/merge_request_feedback objects from the main query that populates the MR widget, and replaces vulnerability_feedback endpoint that is a secondary request.

Things to bear in mind

When implementing this logic, make sure that the finding has a hasMergeRequest and hasIssue fields populated. These are used to render the correct buttons in the modal.

The modal should show a loading spinner while this query is being run.

Verification steps

• Go to gitlab-org/govern/threat-insights-demos/mr-widget-v2-verification!1 (closed)
• Click on a finding
• Try creating an issue, creating an MR, dismissing, undo dismissing

When you reopen the modal, you should see the feedback on the action performed.

Bonus check: refresh the page during these steps to verify whether we really fixed the caching issue (when you dismiss a finding, refreshing the page should still display it as dismissed).