ART: Add forced garbage collection

Add ForceGarbageCollection support to the agent interface.

Add a test.

Test: m test-art-host-run-test-913-heaps
Bug: 32516268
Change-Id: Iaa97520d1b9e4b0adf088ccdf9712193c485b7c5
diff --git a/runtime/openjdkjvmti/OpenjdkJvmTi.cc b/runtime/openjdkjvmti/OpenjdkJvmTi.cc
index 50b50d6..d867727 100644
--- a/runtime/openjdkjvmti/OpenjdkJvmTi.cc
+++ b/runtime/openjdkjvmti/OpenjdkJvmTi.cc
@@ -346,7 +346,7 @@
   }
 
   static jvmtiError ForceGarbageCollection(jvmtiEnv* env) {
-    return ERR(NOT_IMPLEMENTED);
+    return HeapUtil::ForceGarbageCollection(env);
   }
 
   static jvmtiError IterateOverObjectsReachableFromObject(