[feat] allow node adapter to configure listen path

[matths]

The build and run process using the current @sveltejs/adapter-node only allows to run the final node project listening to either host/port or 0.0.0.0/port specified by an environment variable.
I would expect it to allow listening to a path instead as specified by node, check documentation https://nodejs.org/api/net.html#net_server_listen_path_backlog_callback

Use case:
When using a reverse proxy that expects the node application to listen for a path (domain socket file) instead of a host and port, this was currently not available in the node-adapter.
With this pull request I want to make an offer for this missing feature.

With this feature branch applied yo can now do SERVER_PATH=/tmp/socket node build to have your server listen to a domain socket file instead of a port.

I think this is somewhat related to the #1610 as this would be the other attempt to solve this problem. If the node-apapter would lead to a middleware instead of a whole node server, the developer would be free to have his own node server and have it listen to a domain socket file instead of host/port.

Tests
I did clone the existing smoke test for this use case.
And I used the changed adapter-node within my project:

• in packages/adapter-node run pnpn build
• copy files to your project cp packages/adapter-node/index.js packages/adapter-node/index.d.ts packages/adapter-node/files/* ~/myproject/src/lib/
• do an import adapter from './src/lib/adapter-node/index.js';instead of import adapter from '@sveltejs/adapter-node'; in your projects svelte.config.js
• run npm build in your project
• to run your server use SERVER_PATH=/tmp/socket node build

Changeset
I tried to include a changeset, but I am not sure which files to add.

[changeset-bot]

🦋 Changeset detected

Latest commit: a1cbc29

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

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[benmccann]

@matths can you update the PR so that the Lint job passes?

[benmccann]

I think this is somewhat related to the #1610 as this would be the other attempt to solve this problem. If the node-apapter would lead to a middleware instead of a whole node server, the developer would be free to have his own node server and have it listen to a domain socket file instead of host/port.

If you got #2051 merged would you no longer need this PR then? Because I think the more we can expose the underlying to allow users to configure it directly that's better vs trying to add all the options here individually

[matths]

yes, I agree, we can skip and close this PR as I'll focus on #2051.