Add ability to delete files uploaded for settings in admin UI (#13192)

* Allow deleting site uploads

* Refactor and move links into hints

* Fix i18n tests

* Fix HTML output of site_upload_delete_hint

config/routes.rb

@@ -186,6 +186,7 @@ Rails.application.routes.draw do
     end
 
     resource :settings, only: [:edit, :update]
+    resources :site_uploads, only: [:destroy]
 
     resources :invites, only: [:index, :create, :destroy] do
       collection do