ART: Remove runtime.h file_utils.h (iwyu)

It is unnecessary. Fix up transitive includes.

Test: mmma art
Change-Id: Idf25e8df37a3924cc88b5a549b715e9206ca0757
diff --git a/runtime/class_loader_context.cc b/runtime/class_loader_context.cc
index 34fd146..a4aaf13 100644
--- a/runtime/class_loader_context.cc
+++ b/runtime/class_loader_context.cc
@@ -22,6 +22,7 @@
 #include "art_field-inl.h"
 #include "base/casts.h"
 #include "base/dchecked_vector.h"
+#include "base/file_utils.h"
 #include "base/stl_util.h"
 #include "class_linker.h"
 #include "class_loader_utils.h"