Vue 3 Migration - Add Vue 3 migration config for the security dashboard

What does this MR do and why?

Add Vue 3 migration config for the security dashboard

Checklist

• Add the feature flag file
• Add a vue3_migration.yml per entrypoint
• Fix anything the specs or manual testing find
• Add the pipeline:run-rspec-vue3 label to the MR
• Roll out the flag, then set the files to status: migrated

References

• Closes Vue 3 migration: security dashboard (#607919 - closed) • Charlie Kroon • 19.5
• Parent epic: Vue 3 migration: Vulnerability Management and A... (gitlab-org#23064) • Lorenz van Herwaarden • 19.4

Screenshots or screen recordings

Flag combinations

#	Entrypoint	Page	Flag enabled (Vue 3)	Flag disabled (Vue 2)
1	groups/security/dashboard/show	Group security dashboard
2	projects/security/dashboard/index	Project security dashboard
3	security/dashboard/show	Instance security dashboard
4	security/dashboard/settings	Instance dashboard settings
5	organizations/security/dashboard/show	Organization security dashboard	not testable, the route returns 404 in the GDK	not testable

Not covered

Export as PDF, adding and removing monitored projects on the settings page, and the organization entrypoint (its route returns 404 in this GDK).