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/runtime/dex_to_dex_decompiler.h b/runtime/dex_to_dex_decompiler.h
index a2e3f28..93711d1 100644
--- a/runtime/dex_to_dex_decompiler.h
+++ b/runtime/dex_to_dex_decompiler.h
@@ -18,7 +18,7 @@
 #define ART_RUNTIME_DEX_TO_DEX_DECOMPILER_H_
 
 #include "base/array_ref.h"
-#include "dex_file.h"
+#include "dex/dex_file.h"
 
 namespace art {
 namespace optimizer {