ART: Move dex structs into own header

Separating out the structs from DexFile allows them to be forward-
declared, which reduces the need to include the dex_file header.

Bug: 119869270
Test: m
Change-Id: I32dde5a632884bca7435cd584b4a81883de2e7b4
diff --git a/compiler/optimizing/inliner.h b/compiler/optimizing/inliner.h
index 8ac2163..efd4c74 100644
--- a/compiler/optimizing/inliner.h
+++ b/compiler/optimizing/inliner.h
@@ -99,7 +99,7 @@
 
   // Run simple optimizations on `callee_graph`.
   void RunOptimizations(HGraph* callee_graph,
-                        const DexFile::CodeItem* code_item,
+                        const dex::CodeItem* code_item,
                         const DexCompilationUnit& dex_compilation_unit)
     REQUIRES_SHARED(Locks::mutator_lock_);