Removed targetUrl replacing localhost with 127.0.0.1

[DuCanhGH]

What?

Relands #51887, now that it has gone stale.

This fixes the same issue as #52283, but it does that in a different way. Rather than using the provided hostname, we now use exactly what server.address() returns. So if the provided host is localhost, it will return [::1] if IPv6 is used and 127.0.0.1 if IPv4 is used, ensuring that the hostname for the proxy server is always correct.

http://::1:3000 doesn't seem to be a valid URL (browsers doesn't seem to try to resolve this URL), so this PR also changes NextURL so that it handles [::1], rather than ::1. I've also changed the message Listening on port in .next/standalone/server.js so that it displays http://[::1]:3000, rather than http://::1:3000 (this also applies for any other IPv6 hostname).

Why?

This seems to be a better solution and works with IPv6 (some OSes seem to resolve localhost to [::1] instead of 127.0.0.1).

How?

It does that by doing the aforementioned, and also handles IPv6 hostnames in next-server.ts, render-server.ts, next-swc/.../next-request-helpers.ts.

I've ensured that it works with IPv6 hostnames (such as :: and ::1), IPv4 hostnames (such as 127.0.0.1) and localhost.