NextJS: Add experimental RSC support

[shilman]

Closes #21540

What I did

Turns out that in NextJS's version of React, it's possible to render async components in the client using React Suspense.

export default {
  component: MyServerComponent,
  decorators: [(Story) => <Suspense><Story /><Suspense />]
}

To make this ergonomic for NextJS users, I:

• Added an experimental feature flag experimentalNextRSC to add RSC support
• Added a parameter nextjs.rsc to selectively disable RSC on stories/components
• Updated the README with basic documentation on how to use the feature

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

Run the NextJS sandbox and view the sample stories. Observe that both the basic & nested stories work, and that the intentionally erroring stories error in reasonable ways.

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

🦋 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>

[kasperpeulen]

LGTM!