Delete ClassHelper and fix compaction bug in GetDirectInterface

Cleanup helps to prevent compaction bugs. Fixed a fairly serious
compaction error caused by calling ClassHelper::GetDirectInterface
without handling the case where it causes thread suspension due to
ResolveType.

Bug: 8981901

Change-Id: I82b3bb6dd48d21eb6ece7aae0733c4a23c2bc408
diff --git a/runtime/interpreter/interpreter_common.h b/runtime/interpreter/interpreter_common.h
index 9b03334..0c7c8a9 100644
--- a/runtime/interpreter/interpreter_common.h
+++ b/runtime/interpreter/interpreter_common.h
@@ -345,9 +345,9 @@
           self->ThrowNewExceptionF(self->GetCurrentLocationForThrow(),
                                    "Ljava/lang/VirtualMachineError;",
                                    "Put '%s' that is not instance of field '%s' in '%s'",
-                                   ClassHelper(reg->GetClass()).GetDescriptor(),
-                                   ClassHelper(field_class).GetDescriptor(),
-                                   ClassHelper(f->GetDeclaringClass()).GetDescriptor());
+                                   reg->GetClass()->GetDescriptor().c_str(),
+                                   field_class->GetDescriptor().c_str(),
+                                   f->GetDeclaringClass()->GetDescriptor().c_str());
           return false;
         }
       }