Draft: Backend/Frontend integration for Beyond Identity exclusions by groups

What does this MR do and why?

Enables exclusions by Groups on the frontend when adding Beyond identity exclusions.

⚠ changes in this MR are dependent on the backend MRs (!153784, !153785)

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Before	After

How to set up and validate locally

1. Enable the beyond_identity_exclusions feature flag
2. Apply the backend changes:
   • curl https://gitlab.com/gitlab-org/gitlab/-/merge_requests/153784.diff | git apply
   • curl https://gitlab.com/gitlab-org/gitlab/-/merge_requests/153785.diff | git apply
3. Navigate to Admin > Settings > Integrations
4. Click on Beyond Identity > Configure
5. Click on the Exclusions tab
6. Click on Add exclusions to open the Add exclusions Drawer
7. Search and select Groups in the drawer
8. Click on Add exclusions
9. The Group(s) selected in Step 6 should be added to the list of exclusions
10. Removing one or more of the exclusions should remove it from the list

Related to #454372