Delete CodeItemIterator

Replace uses with DexInstructionIterator.

Bug: 63756964
Test: test-art-host-gtest

Change-Id: I28c839c372edcb60583867355d46b14f8752d41b
diff --git a/dex2oat/dex2oat_test.cc b/dex2oat/dex2oat_test.cc
index cb91978..6a2ef1e 100644
--- a/dex2oat/dex2oat_test.cc
+++ b/dex2oat/dex2oat_test.cc
@@ -940,8 +940,8 @@
                class_it.HasNext();
                class_it.Next()) {
             if (class_it.IsAtMethod() && class_it.GetMethodCodeItem() != nullptr) {
-              for (CodeItemIterator it(*class_it.GetMethodCodeItem()); !it.Done(); it.Advance()) {
-                Instruction* inst = const_cast<Instruction*>(&it.CurrentInstruction());
+              for (const DexInstructionPcPair& inst :
+                  class_it.GetMethodCodeItem()->Instructions()) {
                 ASSERT_FALSE(inst->IsQuickened());
               }
             }