Add Vue 3 migration flag for vulnerability report

What does this MR do and why?

Migrate the project, group, and instance vulnerability report pages to Vue 3 (compat mode) behind the vue3_migrate_vulnerability_report feature flag.

This also includes a small fix for the scrolling behavior. With vue 3, the vulnerability report would immediately scroll down the page (and hide the counts) to the list.

References

Related #607916 (closed)

Epic: gitlab-org#23064

How to set up and validate locally

1. Enable the flag: vue3_migrate_vulnerability_report
2. Restart vite: gdk restart vite
3. Open the group, project, and instance vulnerability report and check behavior
4. Validate you see [gitlab] [V] Using Vue.js 3 (with @vue/compat) for VulnerabilityReportRoot in the console