ART: Add GetClassFields support

Add GetClassFields support. Add a test.

Bug: 31684578
Test: m test-art-host-run-test-912-classes
Change-Id: Id7509ef10ec9c19b54b7db8637729556b91273e5
diff --git a/runtime/openjdkjvmti/OpenjdkJvmTi.cc b/runtime/openjdkjvmti/OpenjdkJvmTi.cc
index ddfa96a..b8f1500 100644
--- a/runtime/openjdkjvmti/OpenjdkJvmTi.cc
+++ b/runtime/openjdkjvmti/OpenjdkJvmTi.cc
@@ -560,7 +560,7 @@
                                    jclass klass,
                                    jint* field_count_ptr,
                                    jfieldID** fields_ptr) {
-    return ERR(NOT_IMPLEMENTED);
+    return ClassUtil::GetClassFields(env, klass, field_count_ptr, fields_ptr);
   }
 
   static jvmtiError GetImplementedInterfaces(jvmtiEnv* env,