Associate User with Custom Role in UI

Use Case

As an admin/group owner, I want to assign a custom role to a user so that they can use the custom role I defined.

Requirements

• From any screen where a user can be assigned a role, ensure the custom role(s) are loaded into the dropdown.
• Once a custom role is chosen and assigned to a user, this is saved and the user adopts the new role immediately.
• Ensure a custom role can be set as max role need to figure this one out more
• When inviting members, ensure they can be invited with a custom role:

Open Questions

• From which screens can I assign roles? Behavior should be the same everywhere, but want to verify
• Order of list

Availability & Testing

An e2e test should be added: gitlab-org/quality/testcases#4130 (moved)