MPP-2822: add gtag to Layout and update gaEvent hook to ping both GA endpoints

[groovecoder]

Add GA4

Screenshot

How to test

1. Checkout this branch
2. In frontend/ run npm run dev
3. Go to http://localhost:3000/
   • [ ] In the network inspector, verify a request to www.googletagmanager.com is sent
4. Go to https://analytics.google.com/analytics/web/#/p314403930/realtime/overview
   • [ ] Verify you see your traffic in the realtime report
5. In frontend/ run npm run build
6. In app root, run python manage.py collectstatic
7. In app root, run python manage.py runserver
8. Go to http://127.0.0.1:8000/
   • [ ] In the network inspector, verify a request to www.googletagmanager.com is sent
9. Go to https://analytics.google.com/analytics/web/#/p314403930/realtime/overview
   • [ ] Verify you see your traffic in the realtime report

Checklist (Definition of Done)

• [x] Product Owner accepted the User Story (demo of functionality completed) or waived the privilege.
• [x] ~Customer Experience team has seen or waived a demo of functionality.~
• [x] All acceptance criteria are met.
• [x] Jira ticket has been updated (if needed) to match changes made during the development process.
• [x] I've added or updated relevant docs in the docs/ directory
• [x] Jira ticket has been updated (if needed) with suggestions for QA when this PR is deployed to stage.
• [x] ~All UI revisions follow the coding standards, and use Protocol tokens where applicable (see /frontend/src/styles/tokens.scss).~
• [x] Commits in this PR are minimal and have descriptive commit messages.
• [x] ~l10n changes have been submitted to the l10n repository, if any.~