[lldb] Change setting descriptions to use StringRef instead of ConstString

These probably do not need to be in the ConstString StringPool as they
don't really need any of the advantages that ConstStrings offer.
Lifetime for these things is always static and we never need to perform
comparisons for setting descriptions.

Differential Revision: https://reviews.llvm.org/D148679

lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

@@ -190,8 +190,7 @@ void ObjectFilePECOFF::DebuggerInitialize(Debugger &debugger) {
     const bool is_global_setting = true;
     PluginManager::CreateSettingForObjectFilePlugin(
         debugger, GetGlobalPluginProperties().GetValueProperties(),
-        ConstString("Properties for the PE/COFF object-file plug-in."),
-        is_global_setting);
+        "Properties for the PE/COFF object-file plug-in.", is_global_setting);
   }
 }