Make CodeItem fields private

Make code item fields private and use accessors. Added a hand full of
friend classes to reduce the size of the change.

Changed default to be nullable and removed CreateNullable.
CreateNullable was a bad API since it defaulted to the unsafe, may
add a CreateNonNullable if it's important for performance.

Motivation:
Have a different layout for code items in cdex.

Bug: 63756964
Test: test-art-host-gtest
Test: test/testrunner/testrunner.py --host
Test: art/tools/run-jdwp-tests.sh '--mode=host' '--variant=X32' --debug

Change-Id: I42bc7435e20358682075cb6de52713b595f95bf9
diff --git a/compiler/optimizing/optimizing_unit_test.h b/compiler/optimizing/optimizing_unit_test.h
index 158c252..7d05262 100644
--- a/compiler/optimizing/optimizing_unit_test.h
+++ b/compiler/optimizing/optimizing_unit_test.h
@@ -19,6 +19,7 @@
 
 #include "base/scoped_arena_allocator.h"
 #include "builder.h"
+#include "code_item_accessors-inl.h"
 #include "common_compiler_test.h"
 #include "dex_file.h"
 #include "dex_instruction.h"
@@ -145,7 +146,8 @@
               /* access_flags */ 0u,
               /* verified_method */ nullptr,
               handles_->NewHandle<mirror::DexCache>(nullptr));
-      HGraphBuilder builder(graph, dex_compilation_unit, *code_item, handles_.get(), return_type);
+      CodeItemDebugInfoAccessor accessor(&graph->GetDexFile(), code_item);
+      HGraphBuilder builder(graph, dex_compilation_unit, accessor, handles_.get(), return_type);
       bool graph_built = (builder.BuildGraph() == kAnalysisSuccess);
       return graph_built ? graph : nullptr;
     }