fix: improve Storybook code snippets

[larsrickert]

Relates to #1078, #414

• simplified some Stories
• refactor oynx icon import code transformer to work globally so we don't need to add it to every component that uses icons
• temporarily copy over improved source code generation until it is released in Storybook itself (see Vue: Improve generated code snippets storybookjs/storybook#27194)

Checklist

• The added / edited code has been documented with JSDoc
• A changeset is added with npx changeset add if your changes should be released as npm package (because they affect the library usage)

[changeset-bot]

🦋 Changeset detected

Latest commit: 316b6e1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 7 packages

Name	Type
@sit-onyx/icons	Minor
@sit-onyx/storybook-utils	Major
alpha-test-app	Patch
playground	Patch
sit-onyx	Major
@sit-onyx/chartjs-plugin	Major
@sit-onyx/vitepress-theme	Major

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