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/instrumentation_test.cc b/runtime/instrumentation_test.cc
index 89baa35..836bbe7 100644
--- a/runtime/instrumentation_test.cc
+++ b/runtime/instrumentation_test.cc
@@ -21,7 +21,7 @@
 #include "class_linker-inl.h"
 #include "common_runtime_test.h"
 #include "common_throws.h"
-#include "dex_file.h"
+#include "dex/dex_file.h"
 #include "gc/scoped_gc_critical_section.h"
 #include "handle_scope-inl.h"
 #include "jni_internal.h"