add post count estimates for bulk update requests

app/models/bulk_update_request.rb

@@ -229,4 +229,8 @@ class BulkUpdateRequest < ApplicationRecord
   def is_rejected?
     status == "rejected"
   end
+
+  def estimate_update_count
+    AliasAndImplicationImporter.new(script, nil).estimate_update_count
+  end
 end

app/models/tag_relationship.rb

@@ -192,6 +192,10 @@ class TagRelationship < ApplicationRecord
     end
   end
 
+  def estimate_update_count
+    Post.fast_count(antecedent_name, skip_cache: true)
+  end
+
   extend SearchMethods
   include MessageMethods
 end