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/driver/dex_compilation_unit.cc b/compiler/driver/dex_compilation_unit.cc
index 76e1299..1fe30de 100644
--- a/compiler/driver/dex_compilation_unit.cc
+++ b/compiler/driver/dex_compilation_unit.cc
@@ -16,7 +16,7 @@
 
 #include "dex_compilation_unit.h"
 
-#include "code_item_accessors-inl.h"
+#include "dex/code_item_accessors-inl.h"
 #include "mirror/dex_cache.h"
 #include "utils.h"