[breaking] drop Wrangler 1 support in favour of Wrangler 2

[Rich-Harris]

closes #4885. I don't think there's much of a reason to continue supporting Wrangler 1, given Wrangler 2's overwhelming superiority.

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 pnpx changeset and following the prompts. All changesets should be patch until SvelteKit 1.0

[changeset-bot]

🦋 Changeset detected

Latest commit: 7aa203d

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

This PR includes changesets to release 1 package

Name	Type
@sveltejs/adapter-cloudflare-workers	Patch

Not sure what this means? Click here to learn what changesets are.

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

[ghostdevv]

Wrangler 1 has been EOL for 2 days, might be nice to add something in the readme of the cloudflare adapter(s) about requiring Wrangler 2

[Rich-Harris]

good catch, updated the README

[mglikesbikes]

Hell yes. Rich, thanks. 👌♥️