LibJS: Allow statements to have multiple labels

This is a curious thing that occurs more often than you'd think in
minified JavaScript:

    a: b: c: for (...) { ... break b; ... }

Userland/Libraries/LibJS/Tests/statement-with-many-labels.js

@@ -0,0 +1,9 @@
+test("basic support for statement with many labels", () => {
+    function foo() {
+        a: b: c: for (;;) {
+            break b;
+        }
+        return 1;
+    }
+    expect(foo()).toBe(1);
+});