Upgrade to Yarn Berry (v4)

[tkajtoch]

Summary

Closes #7794.

This PR configures Yarn Berry / Yarn v4 to be used in EUI instead of Yarn Classic.

QA

1. Checkout this PR locally (gh pr checkout 7810), run yarn, and ensure the development server (yarn start) works, and tests (yarn test) pass locally

General checklist

• Browser QA
  • Checked in both light and dark modes
  • Checked in Chrome, Safari, Edge, and Firefox
• Docs site QA
  • Props have proper autodocs (using @default if default values are missing) and playground toggles

[kibanamachine]

Preview staging links for this PR:

• Docs site: https://eui.elastic.co/pr_7810/
• Storybook: https://eui.elastic.co/pr_7810/storybook

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 49ce7a1

History

• 💔 Build #2098 failed de8faa5
• 💔 Build #2094 failed c2507f4
• 💔 Build #2093 failed 80daacb

cc @tkajtoch

[mgadewoll]

🚢 I checked the changes locally and ran the following scripts without issues:

✅ yarn
✅ yarn storybook
✅ yarn start
✅ yarn test
✅ yarn test-visual-regression
✅ yarn build-storybook
✅ yarn build-docs
✅ yarn build-pack