Re-bundle server app in adapter-node

[Conduitry]

Fixes #1257. This makes adapter-node run the server-side app through esbuild as part of the build process, treating anything in (prod) dependencies as external, and bundling everything else. This means that, for example, @sveltejs/kit will no longer need to be installed when deploying the production app - and any other dependencies that the app adds as devDependencies will also be bundled in. This means that, in production, you should be able to copy over your package.json and build/, run npm install --production, and run node build - which is what you'd expect to be able to do.

These changes seem to behave as expected on the project I have at work (which adds a number of dependencies, some of which should be bundled on the server and some of which should not) - but I'd still appreciate some more eyes on this PR.

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

[Conduitry]

I'm not sure whether this is something that we'd expect esbuild to be able to do, but currently with this PR if you import 'foo' where foo is a CommonJS external dependency which has require('util') (or some other Node builtin), then this essentially remains as a require('util') in the output bundle, and is not transformed into an import 'util'.

The CJS helper that esbuild is using and injecting is:

var __require = (x) => {
  if (typeof require !== "undefined")
    return require(x);
  throw new Error('Dynamic require of "' + x + '" is not supported');
};

(and then later on the bundle has __require('util')).

I'm not sure what can be done to make this work other than to have a global.require = createRequire(import.meta.url) at the top of the bundle.

[Conduitry]

I've just push a require() shim of the sort I mentioned above. It's an ugly solution, but I don't know what else we can do without needing changes in esbuild itself. I think this issue is serious enough that we shouldn't wait for upstream changes to more nicely support this, although it would still be a good idea to look through esbuild's open issues and see whether this is on their roadmap.

[bleucitron]

Will this also fix #1428 ?

[Conduitry]

It should. That looks like a duplicate of #1257.