Move step running into enum for dynamic ordering (#1188)

Co-authored-by: Stuart Reilly <sreilly@scottlogic.com>

src/self_update.rs

@@ -3,7 +3,7 @@ use std::env;
 use std::os::unix::process::CommandExt as _;
 use std::process::Command;
 
-use crate::config::Step;
+use crate::step::Step;
 use color_eyre::eyre::{bail, Result};
 use rust_i18n::t;
 use self_update_crate::backends::github::Update;