turbopack: bind server to IPv6 loopback (#47948)
This accomplishes 2 things:
1. binds the turbopack dev server to the IPv6 unspecified address
2. initializes our router with the same hostname/port of the turobpack
server
The first matches the behavior of the Node.js dev server. The IPv6
unspecified address is similar to IPv4's `0.0.0.0` address, allowing us
to accept connection from anywhere. Importantly, it _also_ allows
accepting IPv4 connections, making this address truly universal.
The second means the `request` parameter to any middleware will have the
correct origin, and the request's URL can be used to craft fetch
requests to API endpoints. `new URL(req.url).origin` will be the origin
of the turbopack dev server.
Fixes https://github.com/vercel/turbo/issues/4456
Fixes WEB-855
