Eager load namespace owners for project dashboards

This solves an N+1 query problem where we'd run multiple queries when
getting the namespace owners of the displayed projects.

app/controllers/dashboard/projects_controller.rb

@@ -48,7 +48,7 @@ class Dashboard::ProjectsController < Dashboard::ApplicationController
     ProjectsFinder
       .new(params: finder_params, current_user: current_user)
       .execute
-      .includes(:route, :creator, namespace: :route)
+      .includes(:route, :creator, namespace: [:route, :owner])
   end
 
   def load_events

changelogs/unreleased/dashboards-projects-controller.yml

@@ -0,0 +1,5 @@
+---
+title: Eager load namespace owners for project dashboards
+merge_request:
+author:
+type: other