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/src/components/DatasetContainer/index.tsx

@@ -8,6 +8,7 @@ import {hyphenizeString} from '../../../cypress/integration/common/helpers';
 
 import * as styles from './dsContainer.module.scss';
 import * as METHODOLOGY_COPY from '../../data/copy/methodology';
+import {PAGES_ENDPOINTS} from '../../data/constants';
 
 
 const DatasetContainer = () => {
@@ -43,7 +44,7 @@ const DatasetContainer = () => {
           </Grid>
 
           <div className={styles.returnToTop}>
-            <Link to={`/methodology`}>
+            <Link to={PAGES_ENDPOINTS.METHODOLOGY}>
               {METHODOLOGY_COPY.RETURN_TO_TOP.LINK}
             </Link>
           </div>