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/dexlayout/dex_writer.h b/dexlayout/dex_writer.h
index 3929526..92a002e 100644
--- a/dexlayout/dex_writer.h
+++ b/dexlayout/dex_writer.h
@@ -22,7 +22,7 @@
 #include <functional>
 
 #include "base/unix_file/fd_file.h"
-#include "cdex/compact_dex_level.h"
+#include "dex/compact_dex_level.h"
 #include "dex_ir.h"
 #include "mem_map.h"
 #include "os.h"