Bump vendored fmt library to version 9.1.0

This version properly exports all necessary DLL symbols, eliminating the
need to embed it separately in the Cython module.

ext/SConscript

@@ -40,8 +40,7 @@ if not env['system_fmt']:
     license_files["fmtlib"] = File("#ext/fmt/LICENSE.rst")
     localenv = prep_default(env)
     localenv.Prepend(CPPPATH=Dir('#ext/fmt/include'))
-    libraryTargets.extend(
-        localenv.SharedObject(multi_glob(localenv, 'fmt/src', 'cc')))
+    libraryTargets.extend(localenv.SharedObject(['fmt/src/format.cc', 'fmt/src/os.cc']))
     for name in ('format.h', 'ostream.h', 'printf.h', 'core.h', 'format-inl.h'):
         ext_copies.extend(
             copyenv.Command("#include/cantera/ext/fmt/" + name,

interfaces/cython/SConscript

@@ -45,11 +45,6 @@ for pyxfile in multi_glob(localenv, "cantera", "pyx"):
     cython_obj.append(obj)
 cython_obj.extend(env['python_ext_objects'])
 
-if not env['system_fmt']:
-    # Workaround until we can figure out why all the necessary symbols aren't
-    # being exported from fmt
-    cython_obj.extend(localenv['fmt_targets'])
-
 module_ext = localenv["py_module_ext"]
 ext = localenv.LoadableModule(f"cantera/_cantera{module_ext}",
                               cython_obj, LIBPREFIX="", SHLIBSUFFIX=module_ext,