Indicate locked users in Admin -> Users list view

Proposal

Follow-up to #335032 (closed)

In #335032 (closed) we added (Locked) in the Admin Area user detail view to indicate that a user is locked. We should also add a Locked badge to the Admin Area user list view so the list can be quickly scanned to see which users are locked.

Implementation plan

• Add badges << { text: s_("AdminUsers|Locked"), variant: 'warning' } if user.access_locked? to app/helpers/users_helper.rb#L98
• Add feature spec to spec/features/admin/admin_users_spec.rb#L15