Track call arguments in a single list (#5125)

* Initial implementation of ordered call args

* Run cargo fmt

* Fix some clippy lints

* Add positional len and nth

* Cargo fmt

* Remove more old nth calls

* Good ole rustfmt

* Add named len

Co-authored-by: Hristo Filaretov <h.filaretov@protonmail.com>

crates/nu-command/src/platform/ansi/ansi_.rs

@@ -380,7 +380,9 @@ Format: #
                 None => {
                     return Err(ShellError::UnsupportedInput(
                         String::from("Unknown ansi code"),
-                        call.nth(0).expect("Unexpected missing argument").span,
+                        call.positional_nth(0)
+                            .expect("Unexpected missing argument")
+                            .span,
                     ))
                 }
             }