Allow parse-time evaluation of calls, pipelines and subexpressions (#9499)

Co-authored-by: Antoine Stevan <44101798+amtoine@users.noreply.github.com>

crates/nu-command/tests/commands/path/basename.rs

@@ -81,3 +81,9 @@ fn replaces_basename_of_path_ending_with_double_dot() {
     let expected = join_path_sep(&["some/file.txt/..", "eggs"]);
     assert_eq!(actual.out, expected);
 }
+
+#[test]
+fn const_path_basename() {
+    let actual = nu!("const name = ('spam/eggs.txt' | path basename); $name");
+    assert_eq!(actual.out, "eggs.txt");
+}