Enable log macros to work with no args (#4475)

This is enabled by the C++20 __VA_OPT__ feature.
Uses of "{}" format string were updated.
Some warning suppressions were required for older clang versions.
Also improve codegen of wpi::Logger::Log(), frc::ReportError(), and frc::MakeError();
these generate better and less redundant code if they use fmt::string_view for the
format string instead of templating on it.

wpilibc/src/main/native/cppcs/RobotBase.cpp

@@ -45,7 +45,7 @@ int frc::RunHALInitialization() {
              HALUsageReporting::kLanguage_CPlusPlus, 0, GetWPILibVersion());
 
   if (!frc::Notifier::SetHALThreadPriority(true, 40)) {
-    FRC_ReportError(warn::Warning, "{}",
+    FRC_ReportError(warn::Warning,
                     "Setting HAL Notifier RT priority to 40 failed\n");
   }