Pass Duo pro bulk assignment option to SM code_suggestions frontend

What does this MR do and why?

Resolves: https://gitlab.com/gitlab-org/gitlab/-/issues/467526

We are currently adding abilities for self managed instances also to assign users in bulk through the admin Duo pro UI similar to https://gitlab.com/groups/gitlab-org/-/epics/11463. As the related feature flag that handles the bulk assignment option for SM, was just recently merged !156779 (merged). This MR utilises this new feature flag to pass this value to the frontend for enabling/disabling bulk assignment feature on SM admin section. Only the Frontend part is adjusted through this MR, the backend is to be worked on through a different issue.

Note: This is a follow-up merge request to !156779 (merged)

MR acceptance checklist

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Before	After

How to set up and validate locally

1. Make sure you're running the self-managed gitlab instance with the option, GITLAB_SIMULATE_SAAS=0
2. After logging in as administrator for the instance, visit http://localhost:3000/admin/code_suggestions
3. Enable the feature flags, self_managed_code_suggestions and sm_duo_pro_bulk_user_assignment
4. The FE should display UI elements to be able to bulk assign eligible users.