Fixes #12182 - update default port when server is created

[davidstevens37]

What does this PR do?

This PR sets the default port to 0, which will allow the OS to assign an available ephemeral port when the server is not instructed to use a specific port resolving

Fixes #12182

• Code changes

How did you verify your code works?

• I wrote automated tests
• I ran my tests locally and they pass (build/bun-debug test test/js/node/http/node-http.test.ts)

✓ node:http > createServer > should use the provided port [2.02ms]
✓ node:http > createServer > should assign a random port when undefined [1.47ms]

[Jarred-Sumner]

We cannot change this default in server.zig (nor should we), as that is a breaking change. If you’d like to change this to match node behavior, then it should be changed in node:http

[davidstevens37]

@Jarred-Sumner got it, thanks! Sorry, about that. I wasn't aware that was the default node behavior, just saw an open issue and wanted to support. Love what you're doing here! Just updated it in node:http instead.

Also, any chance you're able to point me in the right direction for #7716? I don't know a thing about Zig, but could be something fun to dig into with when i've got some downtime.

[Electroid]

Thanks for submitting a PR! I leave some minor comments on the tests to make them less flaky.