doc: sort error codes in errors.md

A single exception is that ERR_HTTP2_* comes after ERR_HTTP_*.

Actual content not changed, just some blocks are moved around.

This is a part of the fixes hinted by #21470, which includes some tests
for error codes usage and documentation and enforces a stricter format.

PR-URL: https://github.com/nodejs/node/pull/21485
Refs: https://github.com/nodejs/node/pull/21470


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>