Redesign admin accounts index (#9340)

* Improve overview of accounts in admin UI

- Display suspended status, role, last activity and IP prominently
- Default to showing local accounts
- Default to not showing suspended accounts

* Remove unused strings

* Fix tests

* Allow filtering accounts by IP mask

app/views/admin/accounts/show.html.haml

@@ -68,7 +68,7 @@
               %time.formatted{ datetime: @account.user_current_sign_in_at.iso8601, title: l(@account.user_current_sign_in_at) }
                 = l @account.user_current_sign_in_at
             - else
-              Never
+              \-
       - else
         %tr
           %th= t('admin.accounts.profile_url')