test: add CB4 multi version gadgets integration test

vul/vul-webapp-deserialize/src/test/java/JEXL3ServletTest.java

@@ -0,0 +1,18 @@
+import org.apache.commons.jexl3.*;
+import org.junit.jupiter.api.Test;
+
+/**
+ * @author ReaJason
+ * @since 2025/1/29
+ */
+class JEXL3ServletTest {
+
+    @Test
+    void test() {
+        System.out.println(System.getProperty("java.version"));
+        JexlEngine jexl = new JexlBuilder().create();
+        JexlExpression e = jexl.createExpression("''.getClass().forName('javax.script.ScriptEngineManager').newInstance().getEngineByName('js')");
+        JexlContext jc = new MapContext();
+        System.out.println(e.evaluate(jc));
+    }
+}