Separated orchid-host and orchid-extension

This is an architectural change that allows me to implment specifics first and generalize along observed symmetries in orchid-base

orchid-extension/src/msg.rs

@@ -0,0 +1,6 @@
+use std::io;
+
+use orchid_base::msg::{recv_msg, send_msg};
+
+pub fn send_parent_msg(msg: &[u8]) -> io::Result<()> { send_msg(&mut io::stdout().lock(), msg) }
+pub fn recv_parent_msg() -> io::Result<Vec<u8>> { recv_msg(&mut io::stdin().lock()) }