Create dex subdirectory

Move all the DexFile related source to a common subdirectory dex/ of
runtime.

Bug: 71361973
Test: make -j 50 test-art-host
Change-Id: I59e984ed660b93e0776556308be3d653722f5223
diff --git a/compiler/optimizing/optimizing_unit_test.h b/compiler/optimizing/optimizing_unit_test.h
index 7d05262..661abb1 100644
--- a/compiler/optimizing/optimizing_unit_test.h
+++ b/compiler/optimizing/optimizing_unit_test.h
@@ -19,10 +19,10 @@
 
 #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"
+#include "dex/code_item_accessors-inl.h"
+#include "dex/dex_file.h"
+#include "dex/dex_instruction.h"
 #include "driver/dex_compilation_unit.h"
 #include "handle_scope-inl.h"
 #include "mirror/class_loader.h"