use conduit_fmt::runtime() for runtime string args when we update to fmt 12

[cyrush]

We have similar cases in ascent to these:
llnl/conduit#1578

Compile with gcc13 and c++20 to identify them.

[cyrush]

diff --git a/src/libs/ascent/runtimes/flow_filters/ascent_runtime_vtkh_filters.cpp b/src/libs/ascent/runtimes/flow_filters/ascent_runtime_vtkh_filters.cpp
index 6b5bc82..f9623d2 100644
--- a/src/libs/ascent/runtimes/flow_filters/ascent_runtime_vtkh_filters.cpp
+++ b/src/libs/ascent/runtimes/flow_filters/ascent_runtime_vtkh_filters.cpp
@@ -5435,7 +5435,7 @@ VTKHVTKFileExtract::execute()
           ofs << "!NBLOCKS " << num_global_domains << std::endl;
           for(size_t i=0;i< global_domain_ids.number_of_elements();i++)
           {
-              ofs << conduit_fmt::format(output_file_pattern_rel,
+              ofs << conduit_fmt::format(conduit_fmt::runtime(output_file_pattern_rel),
                                          global_domain_ids[i]) << std::endl;
           }
         }