Allow nested Unstyled usage or escape out of Unstyled

[donaldpipowitch]

Is your feature request related to a problem? Please describe.

Someone in our team wanted to embed a custom component inside MDX that is not affected by Storybook styles, but wrapped in a bigger layout.

Describe the solution you'd like

• It was not obvious why <Unstyled/> didn't fully work. It is explained in the documentation: It should be used as a top-level component and not wrapped in other elements, but there was no feedback. It would be nice if there would be an error/warning at runtime, when <Unstyled/> is not a direct child of DocsContent.
• But... even now that we know it, we'd like to have some part of our component that should show documentation content be shown in Storybook design. Something like DocsContent is not exported however.

// some.mdx
import { Unstyled } from '@storybook/addon-docs/blocks';
import { SomeComponent } from './some-component';

Some text...

<Unstyled>
  <SomeComponent />
</Unstyled>

// some-component.tsx
export const SomeComponent = () => {
  return <SomeLayout>
     <Example />
     <Documentation /> {/* <---- would love to use Storybook style here - maybe <UnUnstyled/> 😅 */}
  </SomeLayout>
}

Describe alternatives you've considered

Allow <Unstyled/> to be nested and not only be used at top-level.

// some.mdx
import { SomeComponent } from './some-component';

Some text...

  <SomeComponent />

// some-component.tsx
import { Unstyled } from '@storybook/addon-docs/blocks';

export const SomeComponent = () => {
  return <SomeLayout>
     <Unstyled><Example /></Unstyled>
     <Documentation /> 
  </SomeLayout>
}

### Are you able to assist to bring the feature to reality?

yes, I can

### Additional context

_No response_