Substitute getUnsafe of shaded protobuf.UnsafeUtil in kafka

Duplicate of the substitution in `GrpcSubstitutions` of the unshaded
class.

Fixes: quarkusio#40100

extensions/kafka-client/runtime/src/main/java/io/smallrye/reactive/kafka/graal/KafkaSubstitutions.java

@@ -1,10 +1,13 @@
 package io.smallrye.reactive.kafka.graal;
 
+import java.lang.reflect.Field;
 import java.lang.reflect.InvocationTargetException;
 
 import com.oracle.svm.core.annotate.Substitute;
 import com.oracle.svm.core.annotate.TargetClass;
 
+import sun.misc.Unsafe;
+
 @TargetClass(className = "org.apache.kafka.common.network.SaslChannelBuilder")
 final class Target_org_apache_kafka_common_network_SaslChannelBuilder {
 
@@ -17,6 +20,20 @@ private static String defaultKerberosRealm() throws ClassNotFoundException, NoSu
 
 }
 
+@TargetClass(className = "org.apache.kafka.shaded.com.google.protobuf.UnsafeUtil")
+final class Target_org_apache_kafka_shaded_com_google_protobuf_UnsafeUtil {
+    @Substitute
+    static sun.misc.Unsafe getUnsafe() {
+        try {
+            Field theUnsafe = Unsafe.class.getDeclaredField("theUnsafe");
+            theUnsafe.setAccessible(true);
+            return (Unsafe) theUnsafe.get(null);
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+}
+
 class KafkaSubstitutions {
 
 }