Remove duplication, split tests

The code move to libdexfile/dex/descriptors_names.cc apparently did not
remove the original code from runtime/utils.cc.  Fix that duplication
and all the header mentions needed.  Also, split the test files to go
along with the new locations for the code to be tested.

Bug: 22322814
Test: make -j 50 checkbuild
      make -j 50 test-art-host-gtest
      flash & boot marlin

Change-Id: Ie734672c4bca2c647d8016291f910b5608674545
diff --git a/runtime/reflection_test.cc b/runtime/reflection_test.cc
index 7794872..7b36c73 100644
--- a/runtime/reflection_test.cc
+++ b/runtime/reflection_test.cc
@@ -22,6 +22,7 @@
 #include "art_method-inl.h"
 #include "base/enums.h"
 #include "common_compiler_test.h"
+#include "dex/descriptors_names.h"
 #include "java_vm_ext.h"
 #include "jni_internal.h"
 #include "nativehelper/scoped_local_ref.h"