HACKING.md seems to be out of date

[BurntSushi]

Discussed in #1057

^{Originally posted by aochagavia August 1, 2023}
I was going through HACKING.md and realized there is some text related to benchmarks that is no longer accurate. Since the file was touched 4 years ago, there might be other things that need updating too.

I'm opening this here because none of the available issue categories seemed fitting.

[BurntSushi]

Yes, indeed, it is outdated. The entire internals were rewritten but I didn't update this document. It probably needs to be completely rewritten.

If you were curious about benchmarks, then see https://github.com/BurntSushi/rebar for more than you could ever possibly want.