Remove ArtCode.

- Instead use OatQuickMethodHeader.
- Various cleanups now that we don't have all those
  ArtMethod -> ArtCode -> OatQuickMethodHeader indirections.

As a consequence of this cleanup, exception handling got a bit
faster.

ParserCombinators benchmark (exception intensive) on x64: (lower is better)
Before:
ParserCombinators(RunTime): 1062500.0 us.
After:
ParserCombinators(RunTime): 833000.0 us.

Change-Id: Idac917b6f1b0dc254ad68fb3781cd61bccadb0f3
diff --git a/runtime/arch/arch_test.cc b/runtime/arch/arch_test.cc
index e676a09..d6ba304 100644
--- a/runtime/arch/arch_test.cc
+++ b/runtime/arch/arch_test.cc
@@ -39,7 +39,7 @@
     runtime->SetInstructionSet(isa);
     ArtMethod* save_method = runtime->CreateCalleeSaveMethod();
     runtime->SetCalleeSaveMethod(save_method, type);
-    QuickMethodFrameInfo frame_info = ArtCode(save_method).GetQuickFrameInfo();
+    QuickMethodFrameInfo frame_info =  runtime->GetRuntimeMethodFrameInfo(save_method);
     EXPECT_EQ(frame_info.FrameSizeInBytes(), save_size) << "Expected and real size differs for "
         << type << " core spills=" << std::hex << frame_info.CoreSpillMask() << " fp spills="
         << frame_info.FpSpillMask() << std::dec;