E2E: Refactor out wait_for_gitlab_to_respond and call after SS toggle

qa/qa/page/main/login.rb

@@ -259,13 +259,10 @@ def sign_in_using_gitlab_credentials(user:, skip_page_validation: false)
           wait_for_gitlab_to_respond
 
           Page::Main::Menu.perform(&:enable_new_navigation) if Runtime::Env.super_sidebar_enabled?
-          Page::Main::Menu.validate_elements_present! unless skip_page_validation
-        end
 
-        def wait_for_gitlab_to_respond
-          wait_until(sleep_interval: 5, message: '502 - GitLab is taking too much time to respond') do
-            has_no_text?('GitLab is taking too much time to respond')
-          end
+          wait_for_gitlab_to_respond
+
+          Page::Main::Menu.validate_elements_present! unless skip_page_validation
         end
 
         def fill_in_credential(user)

qa/qa/support/wait_for_requests.rb

@@ -39,6 +39,12 @@ def finished_loading?(wait: DEFAULT_MAX_WAIT_TIME)
           Capybara.page.has_no_css?('.gl-spinner', wait: wait)
         end
       end
+
+      def wait_for_gitlab_to_respond
+        Waiter.wait_until(sleep_interval: 5, message: '502 - GitLab is taking too much time to respond') do
+          Capybara.page.has_no_text?('GitLab is taking too much time to respond')
+        end
+      end
     end
   end
 end