[EUI+] Reorganize Forms category (WIP)

[cee-chen]

Summary

WIP, placeholder PR

QA

Remove or strikethrough items that do not apply to your PR.

General checklist

• Browser QA
  • [ ] Checked in both light and dark modes
  • [ ] Checked in mobile
  • [ ] Checked in Chrome, Safari, Edge, and Firefox
  • [ ] Checked for accessibility including keyboard-only and screenreader modes
• Docs site QA
  • [ ] Added documentation
  • [ ] Props have proper autodocs (using @default if default values are missing) and playground toggles
  • [ ] Checked Code Sandbox works for any docs examples
• Code quality checklist
  • [ ] Added or updated jest and cypress tests
  • [ ] Updated visual regression tests
• Release checklist
  • [ ] A changelog entry exists and is marked appropriately.
  • [ ] If applicable, added the breaking change issue label (and filled out the breaking change checklist)
• Designer checklist
  • [ ] If applicable, file an issue to update EUI's Figma library with any corresponding UI changes. (This is an internal repo, if you are external to Elastic, ask a maintainer to submit this request)

[kibanamachine]

Preview staging links for this PR:

• Docs site: https://eui.elastic.co/pr_8184/
• Storybook: https://eui.elastic.co/pr_8184/storybook
• New docs: https://eui.elastic.co/pr_8184/new-docs

[elasticmachine]

:green_heart: Build Succeeded

• Buildkite Build
• Commit: 4cab393a26f4c160928a0a639b2f048ea9140f8c