LibJS: break or continue with nonexistent label is a syntax error

Author: https://github.com/mattco98
Commit: e8da5f99b1
Pull-request: https://github.com/SerenityOS/serenity/pull/3724
Issue: https://github.com/SerenityOS/serenity/issues/3714
Reviewed-by: https://github.com/linusg

Libraries/LibJS/Tests/labels.js

@@ -37,3 +37,11 @@ test("labeled for loop with continue", () => {
     }
     expect(counter).toBe(6);
 });
+
+test("invalid label across scope", () => {
+    expect(`
+        label: {
+            (() => { break label; });
+        }
+    `).not.toEval();
+});