du: use "parse_size" from uucore

* fix stderr to be the same than GNU's `du` in case of invalid SIZE

tests/by-util/test_du.rs

@@ -71,6 +71,23 @@ fn _du_basics_subdir(s: &str) {
     }
 }
 
+#[test]
+fn test_du_invalid_size() {
+    new_ucmd!()
+        .arg("--block-size=1fb4t")
+        .arg("/tmp")
+        .fails()
+        .code_is(1)
+        .stderr_only("du: invalid suffix in --block-size argument '1fb4t'");
+    #[cfg(not(target_pointer_width = "128"))]
+    new_ucmd!()
+        .arg("--block-size=1Y")
+        .arg("/tmp")
+        .fails()
+        .code_is(1)
+        .stderr_only("du: --block-size argument '1Y' too large");
+}
+
 #[test]
 fn test_du_basics_bad_name() {
     new_ucmd!()