UI: Removal of experimental components

[ndelangen]

Closes: #23815

What I did

• I've removed the @storybook/components/experimental code & usage.
• I've tried to keep the ArgsTable loading UI intact.
• We'll be adding this experimental UI back in a long lived feature branch, to ensure stability.
• We noticed there's a significant size increase of the static build version of storybook due to the addition of the experimental UI.
• We deemed the above to be not acceptable, and we'll be taking more time to plan this development & rollout.
• I've renamed the legacy directory to components, indicating it won't get replaced.

How to test

• All stories should function as before, though there might be visual changes
• Any visual changes should be as before
• e2e tests should all pass

Checklist

• Make sure your changes are tested (stories and/or unit, integration, or end-to-end tests)
• Make sure to add/update documentation regarding your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli/src/sandbox-templates.ts
• Make sure this PR contains one of the labels below.

["cleanup", "BREAKING CHANGE", "feature request", "bug", "build", "documentation", "maintenance", "dependencies", "other"]

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

[shilman]

LGTM with one small change.

Also I assume you will create a PR into Charles' branch updating from next after you merge this, with merge conflicts removed.