Vue 3 Migrate Integrations pages with vue3_migrate_integrations

What does this MR do and why?

Adds feature flag vue3_migrate_integrations . Verifies that the apps render fine. This covers:

• Admin-level integrations (home page and creation)
• Group integrations (home page and creation)
• Project Integrations (home page and creation)
• Slack setting at the user profile level

Note that the first three (group, admin and project) share same main components, as seen in the directory app/assets/javascripts/integrations.

Also fixes broken page as a result of missing apollo call in a specific integration (Beyond Identity) in app/assets/javascripts/integrations/beyond_identity/components/exclusions_list.vue

References

#613597 (closed)

Screenshots or screen recordings

Before	What it is	After
Unchanged	Admin integrations list
unchanged	Editting/creating admin integration
	Bug in exclusions list
Unchanged	Project level integrations list
Unchanged	GitLab for Slack setting

How to set up and validate locally (Optional)

1. Enable feature flag vue3_migrate_integrations
2. Try to add and/or edit an integration under Admin, Group or Project (for each one it's Settings > Integrations)

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.