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

app/controllers/admin/site_uploads_controller.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+module Admin
+  class SiteUploadsController < BaseController
+    before_action :set_site_upload
+
+    def destroy
+      authorize :settings, :destroy?
+
+      @site_upload.destroy!
+
+      redirect_to edit_admin_settings_path, notice: I18n.t('admin.site_uploads.destroyed_msg')
+    end
+
+    private
+
+    def set_site_upload
+      @site_upload = SiteUpload.find(params[:id])
+    end
+  end
+end