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/dex2oat/dex2oat_test.cc b/dex2oat/dex2oat_test.cc
index b338d08..c91240e 100644
--- a/dex2oat/dex2oat_test.cc
+++ b/dex2oat/dex2oat_test.cc
@@ -30,11 +30,11 @@
 #include "base/macros.h"
 #include "base/mutex-inl.h"
 #include "bytecode_utils.h"
-#include "code_item_accessors-inl.h"
+#include "dex/code_item_accessors-inl.h"
+#include "dex/dex_file-inl.h"
+#include "dex/dex_file_loader.h"
 #include "dex2oat_environment_test.h"
 #include "dex2oat_return_codes.h"
-#include "dex_file-inl.h"
-#include "dex_file_loader.h"
 #include "jit/profile_compilation_info.h"
 #include "oat.h"
 #include "oat_file.h"