Fix #3430: Accept the search[id] param in all controllers.

* Allow every controller to take the `search[id]` param.

* Parse the `search[id]` param the same way that the `id:<N>` metatag is
  parsed. So `search[id]=1,2,3`, `search[id]=<42`, `search[id]=1..10`, for
  example, are all accepted.

app/models/comment.rb

@@ -92,16 +92,12 @@ class Comment < ApplicationRecord
     end
 
     def search(params)
-      q = where("true")
+      q = super
 
       if params[:body_matches].present?
         q = q.body_matches(params[:body_matches])
       end
 
-      if params[:id].present?
-        q = q.where("id in (?)", params[:id].split(",").map(&:to_i))
-      end
-
       if params[:post_id].present?
         q = q.where("post_id in (?)", params[:post_id].split(",").map(&:to_i))
       end