Backport EE E2E protected branch changes

What does this MR do?

EE MR: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/16358

Makes configuring projected branch roles compatible with adding a user or group when using EE.

Adds some login convenience methods.

Allows projects and groups to add members.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content