Fix link to debates help

This link used to open in a new window, and we accidentally changed that
behavior while refactoring it in commit c2710de5f.

Since we're adding a test for this case, and the Proposals::NewComponent
class is similar, we're adding a test for that class too. In the case of
proposals, we need to sign in a user because the proposals form contains
fields to attach image, that currently rely on a user being signed in.

app/components/debates/new_component.html.erb

@@ -2,7 +2,7 @@
   <%= back_link_to debates_path, t("debates.index.section_header.title") %>
 
   <%= header do %>
-    <%= link_to t("debates.new.more_info"), help_path(anchor: "debates") %>
+    <%= new_window_link_to t("debates.new.more_info"), help_path(anchor: "debates") %>
   <% end %>
 
   <aside>