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/OpenjdkJvmTi.cc b/runtime/openjdkjvmti/OpenjdkJvmTi.cc
index d9031ea..9d4b554 100644
--- a/runtime/openjdkjvmti/OpenjdkJvmTi.cc
+++ b/runtime/openjdkjvmti/OpenjdkJvmTi.cc
@@ -277,7 +277,13 @@
                                      jobject initial_object,
                                      const jvmtiHeapCallbacks* callbacks,
                                      const void* user_data) {
-    return ERR(NOT_IMPLEMENTED);
+    HeapUtil heap_util(&gObjectTagTable);
+    return heap_util.FollowReferences(env,
+                                      heap_filter,
+                                      klass,
+                                      initial_object,
+                                      callbacks,
+                                      user_data);
   }
 
   static jvmtiError IterateThroughHeap(jvmtiEnv* env,