ART: Add reference following code

Add FollowReferences support. This is a work in progress.
Specific support for the metadata will be added iteratively.

Add a basic test to 913-heaps.

Bug: 31385354
Test: m test-art-host
Change-Id: I832b05a7397dc96cd9a868020dd7029255f6de87
diff --git a/runtime/openjdkjvmti/ti_heap.h b/runtime/openjdkjvmti/ti_heap.h
index 570dd0c..72ee097 100644
--- a/runtime/openjdkjvmti/ti_heap.h
+++ b/runtime/openjdkjvmti/ti_heap.h
@@ -36,6 +36,13 @@
                                 const jvmtiHeapCallbacks* callbacks,
                                 const void* user_data);
 
+  jvmtiError FollowReferences(jvmtiEnv* env,
+                              jint heap_filter,
+                              jclass klass,
+                              jobject initial_object,
+                              const jvmtiHeapCallbacks* callbacks,
+                              const void* user_data);
+
   static jvmtiError ForceGarbageCollection(jvmtiEnv* env);
 
   ObjectTagTable* GetTags() {