feat: Vite environment API

[eltigerchino]

closes #13692
closes #1712
part of #3535
closes #13739
closes #13357
closes #12637

w.i.p and still has a lot of problems to solve. Needed to open this PR to test installing this from pkg.pr.new since linking locally with pnpm symlinks to the local kit repo. Then, when we try importing kit code from inside an environment, it results in a path which doesn't exist such as /packages/kit/.... Instead, it should probably import from node_modules/@sveltejs/kit/....

This PR adopts the Vite Environment API in kit and changes adapter-cloudflare to use a similar approach to Remix where the user can specify their own worker.js file. Otherwise, we can generate the wrangler config and worker for them. This approach integrates well with vite-plugin-cloudflare and provides users with direct access to the worker script, allowing them to export Durable Objects and add additional handlers.

Thanks to @jamesopstad for #12637 and writing up the Google Doc explaining the Remix and vite-plugin-cloudflare integration. Resources include:

• https://vite.dev/guide/api-environment.html
• https://github.com/cloudflare/workers-sdk/tree/main/packages/vite-plugin-cloudflare
• https://github.com/remix-run/react-router/tree/main/playground/vite-plugin-cloudflare

TODO

• Cloudflare dev
• Cloudflare build
• Node
• vite-plugin-netlify
• Vercel?
• SPA/static?

---

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests

• Run the tests with pnpm test and lint the project with pnpm lint and pnpm check

Changesets

• If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running pnpm changeset and following the prompts. Changesets that add features should be minor and those that fix bugs should be patch. Please prefix changeset messages with feat:, fix:, or chore:.

Edits

• Please ensure that 'Allow edits from maintainers' is checked. PRs without this option may be closed.

[changeset-bot]

⚠️ No Changeset found

Latest commit: ef4d10e

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[changeset-bot]

⚠️ No Changeset found

Latest commit: 71e3d5a

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[benmccann]

You probably need to bump the peer dep version on Vite

[eltigerchino]

You probably need to bump the peer dep version on Vite

Thanks! I missed that. Bumped it to 7 because I think 6 is missing some Environment API behaviour around multiple plugins building the app

[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-14008-svelte.vercel.app/