Make all page endpoints constants

- fix all cypress tests
- refactor all test to use LegacyTests/constants/PAGES_ENDPOINTS
- gatsby-config to use PAGES_ENDPOINTS
- remove ScoreStepList component
- update J40Header to use constants.PAGES_ENDPOINTS
- update snapshots
- there are 3 locations to update PAGES_ENDPOINTS, namely

1. LegacyTests/constants.tsx
2. constants.tsx
3. gatsby-config

client/cypress/integration/LegacyTests/allLinks.spec.js

@@ -1,13 +1,9 @@
 // / <reference types="Cypress" />
 
+import {PAGES_ENDPOINTS} from '../LegacyTests/constants';
+
 describe('Do all the English pages have all links with a defined href attribute?', () => {
-  const pages = [
-    '/',
-    'cejst',
-    'methodology',
-    'contact',
-    'public-engagement',
-  ];
+  const pages = Object.values(PAGES_ENDPOINTS);
 
   pages.forEach((page) => {
     it(`test all href attr on ${page} page`, () => {