Move to using clippy (#1142)

* Clippy fixes

* Finish converting to use clippy

* fix warnings in new master

* fix windows

* fix windows

Co-authored-by: Artem Vorotnikov <artem@vorotnikov.me>

crates/nu-test-support/src/macros.rs

@@ -34,7 +34,7 @@ macro_rules! nu {
             .spawn()
         {
             Ok(child) => child,
-            Err(why) => panic!("Can't run test {}", why.description()),
+            Err(why) => panic!("Can't run test {}", why.to_string()),
         };
 
         let stdin = process.stdin.as_mut().expect("couldn't open stdin");