Fix ls for Windows system files (#5703)

* Fix `ls` for Windows system files

* Fix non-Windows builds

* Make Clippy happy on non-Windows platforms

* Fix new test on GitHub runners

* Move ls Windows code into its own module

crates/nu-command/tests/commands/ls.rs

@@ -391,3 +391,49 @@ fn list_all_columns() {
         );
     });
 }
+
+/// Rust's fs::metadata function is unable to read info for certain system files on Windows,
+/// like the `C:\Windows\System32\Configuration` folder. https://github.com/rust-lang/rust/issues/96980
+/// This test confirms that Nu can work around this successfully.
+#[test]
+#[cfg(windows)]
+fn can_list_system_folder() {
+    // the awkward `ls Configuration* | where name == "Configuration"` thing is for speed;
+    // listing the entire System32 folder is slow and `ls Configuration*` alone
+    // might return more than 1 file someday
+    let file_type = nu!(
+        cwd: "C:\\Windows\\System32", pipeline(
+        r#"ls Configuration* | where name == "Configuration" | get type.0"#
+    ));
+    assert_eq!(file_type.out, "dir");
+
+    let file_size = nu!(
+        cwd: "C:\\Windows\\System32", pipeline(
+        r#"ls Configuration* | where name == "Configuration" | get size.0"#
+    ));
+    assert!(file_size.out.trim() != "");
+
+    let file_modified = nu!(
+        cwd: "C:\\Windows\\System32", pipeline(
+        r#"ls Configuration* | where name == "Configuration" | get modified.0"#
+    ));
+    assert!(file_modified.out.trim() != "");
+
+    let file_accessed = nu!(
+        cwd: "C:\\Windows\\System32", pipeline(
+        r#"ls -l Configuration* | where name == "Configuration" | get accessed.0"#
+    ));
+    assert!(file_accessed.out.trim() != "");
+
+    let file_created = nu!(
+        cwd: "C:\\Windows\\System32", pipeline(
+        r#"ls -l Configuration* | where name == "Configuration" | get created.0"#
+    ));
+    assert!(file_created.out.trim() != "");
+
+    let ls_with_filter = nu!(
+        cwd: "C:\\Windows\\System32", pipeline(
+        r#"ls | where size > 10mb"#
+    ));
+    assert_eq!(ls_with_filter.err, "");
+}