Take compio from the branch skyzen serves on #22

Problem

skyzen serves on a branch of compio that carries changes offered upstream (compio-rs/compio#1140, #1141, #1142 and incremental buffer-ring consumption). A crate that takes compio from crates.io beside it puts a second copy of compio in an application's dependency graph, and compio types from the two copies do not match, so an application on skyzen fails to build.

Scope

Take compio from https://github.com/lexoliu/compio, branch skyzen, the same source http-kit and skyzen use, until upstream releases those changes.

Done when

The crate builds and tests on that branch, and an application depending on skyzen resolves one copy of each compio crate.