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/debug/elf_debug_info_writer.h b/compiler/debug/elf_debug_info_writer.h
index 107ed48..0e11e32 100644
--- a/compiler/debug/elf_debug_info_writer.h
+++ b/compiler/debug/elf_debug_info_writer.h
@@ -260,14 +260,10 @@
 
       // Write local variables.
       LocalInfos local_infos;
-      if (dex->DecodeDebugLocalInfo(accessor.RegistersSize(),
-                                    accessor.InsSize(),
-                                    accessor.InsnsSizeInCodeUnits(),
-                                    accessor.DebugInfoOffset(),
-                                    is_static,
-                                    mi->dex_method_index,
-                                    LocalInfoCallback,
-                                    &local_infos)) {
+      if (accessor.DecodeDebugLocalInfo(is_static,
+                                        mi->dex_method_index,
+                                        LocalInfoCallback,
+                                        &local_infos)) {
         for (const DexFile::LocalInfo& var : local_infos) {
           if (var.reg_ < accessor.RegistersSize() - accessor.InsSize()) {
             info_.StartTag(DW_TAG_variable);