`http_parser` is unmaintained

[itrofimow]

See https://github.com/nodejs/http-parser/issues/522

There is https://github.com/nodejs/llhttp with very similar API (although llhttp is missing the URL parser functions from http-parser), so we could switch to it pretty easily, and it also promises massive perf improvements

[apolukhin]

Sound great. But we have to keep supporting http_parser as long as most of the distros do not get support for the llhttp

[itrofimow]

We can vendor it in third_party, and thats what most people who switched do - llhttp has c sources in releases .tar since v6 or smth, so it should be as easy as FetchContent: https://github.com/nodejs/llhttp#using-with-cmake

[itrofimow]

Addressed by https://github.com/userver-framework/userver/commit/e6b635c1a0ee2c2a70f9bd909c478f14c8df82c8