chore: migrate from esbuild to rolldown

[teemingc]

closes #15424
closes #13609

This PR switches the Vercel and Netlify adapters to use rolldown instead of esbuild
It also updates the build targets from es2020 to es2022 to support top-level await

I also made the Vercel adapter run the test app build after the unit tests just because it's a quick and cheap way to verify the build runs if we don't run platform tests.

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🦋 Changeset detected

Latest commit: d0f0109

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

This PR includes changesets to release 2 packages

Name	Type
@sveltejs/adapter-netlify	Major
@sveltejs/adapter-vercel	Major

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-15432-svelte.vercel.app/

[benmccann]

this looks great!