chore(storybook): remove storybook

[rexxars]

Description

This PR removes the @sanity/storybook module, the storybook "example" and the server initializer hook used to start the storybook server on development server start.

The storybook integration hasn't been maintained for a while, and seems to have broken a while back. Given that we are not using it ourselves or adding stories to it, we don't want to keep maintaining it. In the future, we'll expose more components and building blocks through the sanity workshop/arcade/similar.

Once this PR has been merged, I will publish a 2.18.1 release of the storybook module which replaces the package with an empty tool notifying the user that the plugin has been taken out of maintenance and should be removed. I'll also mark the module as deprecated on npm.

What to review

• Does the studio still build as it should?
• Are there any remnants laying around (I intentionally kept the part stubs around in case someone has implemented a story)
• Are there any more aspects we need to cover before doing this change?

Notes for release

• Removed the non-functioning storybook integration

[vercel]

This pull request is being automatically deployed with Vercel (learn more).
To see the status of your deployments, click below or on the icon next to each commit.

perf-studio – ./

🔍 Inspect: https://vercel.com/sanity-io/perf-studio/4DdDJJSHH4Yu9opqXd6HCpeyLbvn
✅ Preview: https://perf-studio-git-chore-remove-storybook.sanity.build

test-studio – ./

🔍 Inspect: https://vercel.com/sanity-io/test-studio/2GhptpCv1YQi7jGUQc2BSJJtbWhq
✅ Preview: https://test-studio-git-chore-remove-storybook.sanity.build