Convert FileNotFound to named fields (#11120)

# Description

Part of #10700

# User-Facing Changes

None

# Tests + Formatting

- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- 🟢 `toolkit test`
- 🟢 `toolkit test stdlib`

# After Submitting

N/A

crates/nu-command/src/system/nu_check.rs

@@ -117,7 +117,9 @@ impl Command for NuCheck {
                             if let Some(path) = path {
                                 path
                             } else {
-                                return Err(ShellError::FileNotFound(path_str.span));
+                                return Err(ShellError::FileNotFound {
+                                    span: path_str.span,
+                                });
                             }
                         }
                         Err(error) => return Err(error),