Reuse admin search component in other sections

There are some sections where we are not reusing it:

* The budget investments search is completely different, so this
  component isn't appropriate there
* Booth assignment and officers are slightly different, and I'm not
  entirely sure it's safe to refactor these cases

app/views/admin/debates/index.html.erb

@@ -5,7 +5,10 @@
 <h2><%= t("admin.debates.index.title") %></h2>
 
 <% if @debates.any? %>
-  <%= render "/admin/shared/debate_search", url: admin_debates_path %>
+  <%= render Admin::SearchComponent.new(
+    url: admin_debates_path,
+    label: t("admin.shared.debate_search.placeholder")
+  ) %>
 
   <h3 class="inline-block"><%= page_entries_info @debates %></h3>