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/art_method.cc b/runtime/art_method.cc
index efdf599..bbc6007 100644
--- a/runtime/art_method.cc
+++ b/runtime/art_method.cc
@@ -25,6 +25,7 @@
 #include "base/stringpiece.h"
 #include "class_linker-inl.h"
 #include "debugger.h"
+#include "dex/descriptors_names.h"
 #include "dex/dex_file-inl.h"
 #include "dex/dex_file_exception_helpers.h"
 #include "dex/dex_instruction.h"