Replace StackHandleScopeCollection with VariableSizedHandleScope

VariableSizedHandleScope's internal handle scopes are not pushed
directly on the thread. This means that it is safe to intermix with
other types of handle scopes.

Added test.

Test: clean-oat-host && test-art-host

Change-Id: Id2fd1155788428f394d49615d337d9134824c8f0
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 874c1ed..1e69966 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -35,7 +35,7 @@
 // double).
 static constexpr bool kEnableFloatingPointStaticEvaluation = (FLT_EVAL_METHOD == 0);
 
-void HGraph::InitializeInexactObjectRTI(StackHandleScopeCollection* handles) {
+void HGraph::InitializeInexactObjectRTI(VariableSizedHandleScope* handles) {
   ScopedObjectAccess soa(Thread::Current());
   // Create the inexact Object reference type and store it in the HGraph.
   ClassLinker* linker = Runtime::Current()->GetClassLinker();