[chore] update adapters to esbuild 0.15

[Conduitry]

I was wondering why my project's lockfile had gotten so much longer after a recent upgrade, and at least part of the reason is that Vite 3.1.0 is bringing in esbuild 0.15 and the adapters are bringing in 0.14. This updates all of the adapters to ^0.15.6, the same range as Vite currently uses.

While I was at it, I also updated some dev deps on Vite throughout this repo from the 3.1.0 beta to ^3.1.0, so we don't have two versions of Vite getting installed.

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[changeset-bot]

🦋 Changeset detected

Latest commit: bbc4e4e

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

This PR includes changesets to release 7 packages

Name	Type
@sveltejs/adapter-cloudflare	Patch
@sveltejs/adapter-cloudflare-workers	Patch
@sveltejs/adapter-netlify	Patch
@sveltejs/adapter-node	Patch
@sveltejs/adapter-vercel	Patch
create-svelte	Patch
@sveltejs/adapter-auto	Patch

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[benmccann]

we should probably add create-svelte to the changelog as well

[Conduitry]

This isn't the package.json that's used when people run the CLI. That's package.template.json, which was already updated.

[Conduitry]

The change to the changeset in bbc4e4e was not correct. This doesn't update any user-visible dependencies to Vite 3.1.0, and doesn't affect what create-svelte creates. I've reverted it in b68f242.