Bundle non-prod dependencies with esbuild

[Rich-Harris]

This closes #3176, by always bundling dev dependencies using esbuild. Supersedes #6301.

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. All changesets should be patch until SvelteKit 1.0

[changeset-bot]

🦋 Changeset detected

Latest commit: cf6bfa2

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-node	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

[benmccann]

It's probably worth adding something to the adapter-node readme saying that devDependencies will be bundled and dependencies will not so that people know what to put where

[gterras]

It's probably worth adding something to the adapter-node readme saying that devDependencies will be bundled and dependencies will not so that people know what to put where

Also maybe a general note explaining the difference since it's less obvious than a common node project, like the Sapper docs did.

[AlexRMU]

What about minification of the entire server part and bundling of prod dependencies?

[Rich-Harris]

There's really nothing to be gained from minifying server-side code except making it harder to debug. As the README says, if you want a dependency to be bundled, move it to devDependencies

[AlexRMU]

My build weighs 120 MB, which is 3 times more than node 16 alpine. It's sad. You can make minification optional.