tests: Move run-pass tests without naming conflicts to ui

src/test/ui/for-loop-while/loop-label-shadowing.rs

@@ -0,0 +1,11 @@
+// run-pass
+// Issue #12512.
+
+// pretty-expanded FIXME #23616
+
+fn main() {
+    let mut foo = Vec::new();
+    'foo: for i in &[1, 2, 3] {
+        foo.push(*i);
+    }
+}